docs.daveops.net

Snippets for yer computer needs

Programming Languages

C

Install tooling in Fedora

sudo yum groupinstall "C Development Tools and Libraries"

Resources

Misc Notes

Open and read file

const char *filename = "file.txt";
unsigned char byte;
FILE *fp;

fp = fopen(filename, "rb");

if (!fp) {
        printf("Couldn't open file\n");
        return 1;
}

while(!feof(fp)) {
        fread(&byte, sizeof(int), 1, fp);
        printf("%i\n",byte);
}

fclose(fp);

glibc

Get version

/lib/libc.so.6

or

#include <stdio.h>
#include <gnu/libc-version.h>
int main (void) { puts (gnu_get_libc_version ()); return 0; }

Go

Syntax cheatsheet

package main

import (
    "fmt"
    "os"
    "bufio"
)

func read_file(path string) string {
        f, err := os.Open(filearg)
        if err != nil {
                panic(err)
        }
    scanner := bufio.NewScanner(f)
    for scanner.Scan() {
        fmt.Println(scanner.Text())
    }
}

func main() {
        fmt.Println("hello world")
}

Go modules

go mod init <module_name>
go mod vendor
go get -u

Cross-compilation

# Compile for AMD64 Linux
GOOS=linux GOARCH=amd64 go build

https://golang.org/doc/install/source#environment

Static linking

If you’re not using CGo, you can statically link with CGO_ENABLED.

In Fedora this appears to be on by default

CGO_ENABLED=0 go build

Resources

godoc -http=:8080

Looking into

Templating

{{/* comment */}}  Defines a comment
{{.}}              Renders root element
{{.Foo}}           Renders the "Foo"-field in a nested element

{{if .Done}} {{else}} {{end}}   Defines an if-statement
{{range .Items}} {{.}} {{end}}  Loops over all “Items” and renders each using {{.}}
{{block "bar" .}} {{end}}       Defines a block with the name "bar"

Go - FastCGI

package main

import (
    "fmt"
    "net/http"
    "net/http/fcgi"
)

func hello(w http.ResponseWriter, r *http.Request) {
    fmt.Fprintln(w, "Hello")
}

func main() {
    http.HandleFunc("/", hello)

    err := fcgi.Serve(nil, nil)
    if err != nil {
        panic(err)
    }
}

Mage

https://magefile.org/

Java

Types

type note
byte 8-bit signed two’s complement integer
short 16-bit signed two’s complement integer
int 32-bit signed two’s complement integer
long 64-bit two’s complement integer
float single-precision 32-bit IEEE 754 floating point
double double-precision 64-bit IEEE 754 floating point
boolean the size isn’t precisely defined

Numeric literals

You can use underscore characters in SE7+ example: long hexBytes = 0xFF_CC_DA_B5;

AES intrinsics

Requires Java 8 and Intel 2010+ Westmere

-XX:+UseAES -XX:+UseAESIntrinsics

Zero copy

Avoid copying the file data across user/kernel boundary, instead have the kernel put the file in a buffer and use DMA to pass the data directly.

https://www.ibm.com/developerworks/linux/library/j-zerocopy/

SSL

Debugging

# print each handshake message
java -Djavax.net.debug=ssl:handshake MyApp

Maven

https://maven.apache.org/what-is-maven.html

zig

https://ziglang.org/

Versions:

CLI

# Get Clang version
zig cc --version
# Get compilable targets
zig targets

Julia

https://julialang.org/

Forth

words action
. pop an element off the stack
.s display the contents of stack
drop drop top of stack
 … comment
see decompile
words action
include includes a forth source file

colon definitions

: funcname ( stack effect comment )
  do stuff ;

\ local variables
: funcname { a b -- b a }
  b a ;

Kotlin

http://kotlinlang.org/

Prolog

https://bernardopires.com/2013/10/try-logic-programming-a-gentle-introduction-to-prolog/

Tcl

Tcl

Syntax cheatsheet


 if {blah == 0} {
 # blah
 } elseif {blah == 1} {
 # blah!
 } else {
 # blah?
 }

 switch xyz {
 a
-  #drop into next block
 b {
 format 1
 }
 default {
 format 3
 }
 }   # returns 3

 set false 0
 set true 1

Namespaces

namespace eval blah {}

Profiling statements

puts "unbraced: [time { expr 15 * 20 } 1000]"
puts "braced:   [time { expr {15 * 20} } 1000]"

Disassemble statement

This is fun, because it shows just how much of a difference there is in optimizing statements

::tcl::unsupported::disassemble script {expr $a eq $b}
::tcl::unsupported::disassemble script {expr {$a eq $b}}

Creating tests

package require tcltest
namespace import ::tcltest::*

# Software under test
source sum.tcl

test sum_addTwoZerosExpectZero {
Test: [sum 0 0] == 0
} -body {
sum 0 0
} -result 0

test sum_addTwoPositiveNumbers {} -body {
sum 4 9
} -result 13

test sum_addPositiveToNegative {} -body {
sum -95 72
} -result -23

cleanupTests

OpenACS

ad_proc documentation metadata

Return a file

set file [open $file_path "r"]
ns_set update [ns_conn outputheaders] content-disposition "attachment; filename=$filename"
ns_returnfile 200 [ns_guesstype $file] $file_path

Make your OpenACS form’s checkbox be selected by default

In ad_page_contract:

{fries "t"}

In ad_form:

{fries:text(checkbox),optional
        {label {"Would you like fries with that?"}}
        {html {[if {$fries=="t"} {return "checked checked"}]}}
        {options {{"" t}}}
}

ADP tags

<if @datasource.variable@ eq "blue">
      <td bgcolor=#0000ff>
</if>
<elseif @datasource.variable@ eq "red">
      <td bgcolor=red>
</elseif>
<else>
      <td bgcolor=#ffffff>
</else>

Objective C

Classes

Categories extend classes

Interface

/* #import is like #include, but only included once during compilation */
#import "thing.h"

@interface MyClass : SuperClass <XYZProto, AnotherProtocol> {
  int integerInstanceVariable;
}
+ (void)aClassMethod;
- (void)anInstanceMethod;

@property NSString *name;
@property NSNumber *year_a;
@property int year_b;
@property (readonly) int readonly_year;
// you can change the getter method name by changing the attribute
@property (getter=isFinished) BOOL finished;

@end

Implementation

// If you enable modules for iOS >= 7.0 or OS X >= 10.9 projects in
// Xcode 5 you can import frameworks with @import
@import Foundation;

#import "myclass.h"

@implementation MyClass {
  int integerInstanceVariable;
}

// If you want to change the instance variable name, use @synthesize
@synthesize year_a = ivar_yeara;

+ (void)aClassMethod {
  NSLog(@"This is an Objective-C string literal");
}
- (void)anInstanceMethod {
  // Set an instance variable
  _name = @"Doug E Fresh";
  // Though it's better to use accessor methods / dot syntax
  self.name = @"Fresh Prince";
}
@end

MyClass *thing = [[MyClass alloc] init]
// or, if you're not providing arguments to initialize
MyClass *thing = [MyClass new]

Objects

// setter methods are set + property name
[person setFirstName:@"Bob"];
// or use dot syntax
person.firstName = @"Bob";

Protocols

@protocol XYZProto
// by default methods are required
- (NSUInteger) numOfThings;
@optional
// Everything after @optional is optional, unless there's a @required after that
- (NSString *) stringThing;
@end

NSString *someString;
if ([self.dataSource respondsToSelector:@selector(stringThing)]) {
    someString = [self.dataSource stringThing];
}

// to inherit a protocol
@protocol XYZProto <NSObject>

@end

Collections

Arrays

// Trailing nil needed
NSArray *someArray = [NSArray arrayWithObjects:firstObject, secondObject, thirdObject, nil];
// Easier to read literal syntax (no trailing nil needed)
NSArray *someArray = @[firstObject, secondObject, thirdObject];

if ([someArray count] > 0) {
    NSLog(@"First item is: %@", [someArray objectAtIndex:0]);
    // or
    NSLog(@"First item is: %@", someArray[0]);
}

Dictionaries

NSDictionary *dictionary = @{
              @"anObject" : someObject,
           @"helloString" : @"Hello, World!",
           @"magicNumber" : @42,
                @"aValue" : someValue
};

NSNumber *storedNumber = [dictionary objectForKey:@"magicNumber"];
// or
NSNumber *storedNumber = dictionary[@"magicNumber"];

Blocks

Like closures/lambdas in other languages

^{ NSLog(@"It's a block!"); }

Error Handling

Error Handling Programming Guide for Cocoa

NSString *domain = @"net.daveops.MyApplication.ErrorDomain";
NSString *desc = NSLocalizedString(@"Unable to…", @"");
NSDictionary *userInfo = @{ NSLocalizedDescriptionKey : desc };

NSError *error = [NSError errorWithDomain:domain
                                     code:-101
                                 userInfo:userInfo];

Exceptions

@try {
    // do something that might throw an exception
}
@catch (NSException *exception) {
    // deal with the exception
}
@finally {
    // optional block of clean-up code
    // executed whether or not an exception occurred
}

i18n

NSLocalizedString strings
NSNumberFormatter numerical values
NSDateFormatter format dates
NSLocale  

Perl

Syntax Cheatsheet

#!/usr/local/bin/perl -wT
use strict

$scalar = 0;
@array = [1,2,3];

if (expr) block elsif (expr) block else block;

sub hw {
  print "Hello World"
}

hw();

LWP - HTTP Get

get($url)

To save to a file

getstore($url, $file)

See if LWP is installed

perl -MLWP -le "print(LWP->VERSION)"

Parsing JSON

use JSON;
decode_json($json);

Smalltalk

http://www.smalltalk.org

Strongtalk (Smalltalk with a strong static type system)

Pharo

“R”

https://www.r-project.org/

Syntax cheatsheet

# create a vector
things <- c('foo', 'bar', 'baz')

plotting

bar chart

png(file="output.png")
barplot(vector,names.arg=vector_of_names, xlab="groups", ylab="frequency")
dev.off()

import a CSV

dat <- read.csv(file="foobar.csv", header=TRUE, sep=",")

COBOL

Fortran

ML

https://www.cl.cam.ac.uk/~lp15/MLbook/pub-details.html

Erlang

Shell

help().
q().

f(Variable). % drop a variable
f(). % drop all variables

Syntax cheatsheet

% division
5 / 2.
5 div 2.
5 rem 2.

% base conversion
2#1010. % is base 2 for 10

% equality
1 =:= 1. % returns true
1 =/= 0. % returns true

swift

Benefits

Variables initialized before use

CLI

swift - start up a Swift REPL (backed by LLDB)

swiftc - compile swift code

Syntax cheatsheet

No semicolons needed

No main() needed, global scope is entry point

Values are never implicitly converted to another type

String interpolation: “The building is (feet) feet tall”

let multi_line_string = """
multi
line
string
"""

let dictionary = [
  "hotpotato": 1,
  "coldpotato" 2
]

let empty_dict = [:]

if boolean_var {
  print("this is true")
}

var optionalString: String? = "Maybe hello?"

PHP

Run a server instance with a script

Requires PHP >= 5.4 - http://php.net/manual/en/features.commandline.webserver.php

php -S localhost:8000 router.php

Datestamps

<?php
//mktime(hour,minute,second,month,day,year)

echo date("Y/m/d", mktime(0,0,0,11,11,2011));
//2011/11/11
?>

Autogenerate a file download

<?php
header("Content-Type: text/calendar; charset=utf-8");
header("Content-Disposition: attachment; filename=test.ics");
// render file...

Turn off error reporting

<?php
error_reporting(0)
?>

Check if domain resolves

<?php
checkdnsrr($host)
?>

Authenticating users

<?php
session_start();
// Check for session injection
if (isset($_REQUEST['_SESSION'])) {
    session_destroy();
    die('');
} elseif (isset($_SESSION['HTTP_USER_AGENT'])) {
    if ($_SESSION['HTTP_USER_AGENT'] != md5($_SERVER['HTTP_USER_AGENT'])) {
     session_destroy();
     die('');
    }
}
// At end of page, let's regenerate the session ID
if(isset($_SESSION['username'])) {
    session_regenerate_id(TRUE);
} 
?>

Validation

<?php
// Numeric validation
is_int($var)
is_numeric($var)
?>

Export to CSV

<?php
header("Expires: 0");
header("Cache-control: private");
header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
header("Content-Description: File Transfer");
header("Content-Type: text/csv");
header("Content-disposition: attachment; filename=rawlogs.csv");
?>

Get filename

<?php
$FILE_NAME = basename($_SERVER["PHP_SELF"]);
?>

Return multiple values

<?php
function mult() {
    return array(0, 1);
}

list ($zero, $one) = mult();
?>

Create an array of objects

<?php
$allCars=array();
$result = mysql_query($SQL);

while ($rowInfo = mysql_fetch_assoc($result))
{ 
     $tempCar=new Car();

     $tempCar->setMake($rowInfo['car_make']);
     $tempCar->setModel($rowInfo['car_model']);
     $tempCar->setColor($rowInfo['car_color']);

     $allCars[]=$tempCar;
}
?>

Include PEAR (Dreamhost)

<?php
//Include my PEAR path
set_include_path("." . PATH_SEPARATOR . ($UserDir = dirname($_SERVER['DOCUMENT_ROOT'])) . "/pear/php" . PATH_SEPARATOR . get_include_path());
?>

Scrape $_GET parameters

If mod_rewrite or some other mechanism is preventing the filling of the $_GET array, use this:

<?php
parse_str($_SERVER['QUERY_STRING'], $_GET);
?>

Convert command line arguments into GET variables

<?php
parse_str(implode('&amp;', array_slice($argv, 1)), $_GET);
?>

Get PHP config info

# Get configuration (like phpinfo())
php -i
# Get location of php.ini
php --ini

Redirect to a different URL

<?php
header("Location: https://example.org/"); 
?>

Syntax cheatsheet

<?php
if ($blah == 0) {
  // code
} elseif ($blah == 1) {
  // code
} else {
  // code
}

// null coalescing - ??
// $var = isset($_GET['var']) ? $_GET['var'] : 'default';
$var = $_GET['var'] ?? 'default';

$arr = array(1, 2, 3, 4);
foreach ($arr as $value) {
        print $value;
}

switch ($blah) {
  case 0:
        // code
        break;
  case 1:
        // code
        break;
  default:
        // code
        break;
}

function foo () {
  return 0;
}
?>

composer

Composer homepage

Require a package

composer require repo/package

Will drop composer.json and composer.lock

Load vendor directory

<?php
require __DIR__ . '/vendor/autoload.php';

Insecurity

PHP has more than a few security pitfalls, this is just a quick list of ways it can bite you.

$FILES tmp_name usage

tmp_name is untrusted input and should be sanitized before doing any file operations (like move_uploaded_file)

exif_imagetype is not validation

If you’re testing a file to ensure it’s an image, exif_imagetype alone is inadequate, as it can be easily bypassed with a magic string like “BM” (for bitmap)

PDO

// simple query
<?php
$sql = "SELECT max(id) FROM table";
$sth = $DB->prepare($sql);
$sth->execute();
$max_id= $sth->fetchColumn();
?>

Versions

8.1

Binary

Read a binary file

<?php
$handle = fopen('/path/to/file', 'rb');
$contents = fread($handle, filesize($filename));
fclose($handle);
?>

Binary craziness

<?php
bindec();
decbin();
?>

Playing with endianness

<?php
// For changing endianness, just use strrev()
// %016b for 16-bit, %032b for 32-bit
strrev(sprintf("%016b", $int));
?>

Unpacking binary file formats

<?php
// For parsing binary file formats,
// use pack/unpack
function get_gif_header($image_file)
{

    /* Open the image file in binary mode */
    if(!$fp = fopen ($image_file, 'rb')) return 0;

    /* Read 20 bytes from the top of the file */
    if(!$data = fread ($fp, 20)) return 0;

    /* Create a format specifier */
    $header_format = 
            'A6Version/' . # Get the first 6 bytes
            'C2Width/' .   # Get the next 2 bytes
            'C2Height/' .  # Get the next 2 bytes
            'C1Flag/' .    # Get the next 1 byte
            '@11/' .       # Jump to the 12th byte
            'C1Aspect';    # Get the next 1 byte

    /* Unpack the header data */
    $header = unpack ($header_format, $data);

    $ver = $header['Version'];

    if($ver == 'GIF87a' || $ver == 'GIF89a') {
        return $header;
    } else {
        return 0;
    }
}

/* Run our example */
print_r(get_gif_header("aboutus.gif"));

/*
Array
(
    [Version] => GIF89a
    [Width1] => 97
    [Width2] => 0
    [Height1] => 33
    [Height2] => 0
    [Flag] => 247
    [Aspect] => 0
)
*/
?>

Barcodes

Get a UPC check digit

<?php
function get_ean_checkdigit($barcode){
        $sum = 0;
        for($i=(strlen($barcode));$i>0;$i--){
         $sum += (($i % 2) * 2 + 1 ) * substr($barcode,$i-1,1);
        }
        return (10 - ($sum % 10));
}
?>

Create a barcode with Image_Barcode2 (PEAR)

<?php
require_once 'Image/Barcode2.php';
$bc = new Image_Barcode2;
$bc->draw($_GET['bctext'], "int25", "png");
?>

SQLite

Initializing

<?php
/**
 * Simple example of extending the SQLite3 class and changing the __construct
 * parameters, then using the open method to initialize the DB.
 */
class MyDB extends SQLite3
{
    function __construct()
    {
        $this->open('mysqlitedb.db');
    }
}

$db = new MyDB();

$db->exec('CREATE TABLE foo (bar STRING)');
$db->exec("INSERT INTO foo (bar) VALUES ('This is a test')");

$result = $db->query('SELECT bar FROM foo');
var_dump($result->fetchArray());
?>

Reading values

<?php
//read data from database
$query = "SELECT * FROM Movies";
if($result = $database->query($query, SQLITE_BOTH, $error))
{
  while($row = $result->fetch())
  {
    print("Title: {$row['Title']} <br />" .
          "Director: {$row['Director']} <br />".
          "Year: {$row['Year']} <br /><br />");
  }
}
else
{
  die($error);
}
?>

node.js

NodeJS ECMAScript Support

Debugging

node --inspect ...

Can also be turned on with SIGUSR1

Node <7 - Debugger API

Node >8 - Inspector API

Debugger

Connect with node inspect HOST:PORT

Debug directly with node inspect file.js

Inserting debugger; in your code sets a breakpoint

Stepping

cont, c Continue execution
next, n Step next
step, s Step in
out, o Step out
pause Pause running code (like pause button in Developer Tools)

Breakpoints

setBreakpoint(), sb() Set breakpoint on current line
setBreakpoint(line), sb(line) Set breakpoint on specific line
setBreakpoint(‘fn()’), sb(…) Set breakpoint on a first statement in functions body
setBreakpoint(‘script.js’, 1), sb(…) Set breakpoint on first line of script.js
clearBreakpoint(‘script.js’, 1), cb(…) Clear breakpoint in script.js on line 1

Information

backtrace, bt Print backtrace of current execution frame
list(5) List scripts source code with 5 line context (5 lines before and after)
watch(expr) Add expression to watch list
unwatch(expr) Remove expression from watch list
watchers List all watchers and their values (automatically listed on each breakpoint)
repl Open debugger’s repl for evaluation in debugging script’s context
exec expr Execute an expression in debugging script’s context

Execution control

run Run script (automatically runs on debugger’s start)
restart Restart script
kill Kill script

Various

| scripts | List all loaded scripts
| version | Display V8's version

Rust

Writing tests

If the function passes, the test passes

#[test]
fn this_tests_code(){
  println!("");
  if 1 == 0 {
    fail!("This should never happen");
  }
}

To compile the tests and replace main with test runner:

rustc --test test.rs

https://doc.rust-lang.org/stable/book/testing.html

Syntax cheatsheet

//! You can create a description for your crate using two slashes and an exclamation mark

// Add debugging info to struct
// Trait is std::fmt::Debug
/// Documentation comments use three slashes and Markdown
#[derive(Debug)]
struct Rectangle {
    width: u32,
    height: u32,
}

// use impl (implementation) block to create methods
impl Rectangle {
  fn area(&self) -> u32 {
    self.width * self.height
  }
  fn is_square(&self) -> bool {
    self.width == self.height
  }
  // associated functions
  #[allow(dead_code)]
  fn square(size: u32) -> Rectangle {
    Rectangle { width: size, height: size }
  }
}

fn main() {
  let mut a = 1; // mut makes the value mutable
  println!("{}", a);
  a = 2;
  println!("{}", a);

  // shadowing
  let x = 2;
  let x = x + 2;

  eprinln!("Use this to print to stderr");

  loop {
    println!("simple loop");
    break;
  }

  println!("easy as");
  for number in 1..4 {
    println!("{}", number);
  }

  let rect = Rectangle { width: 10, height: 20 };
  // get struct details for debugging
  println!("rect is {:?}", rect);
  println!("pretty print rect is {:#?}", rect);

  // using match
  let thing = 5;
  match thing {
     5 => println!("five!"),
     6 => {
         println!("six?");
         println!("why six?");
     },
     _ => (), // wildcard, don't do anything
  }
  // or using if let
  if let 5 = thing {
    println!("still five");
  } else {
    println!("not five");
  }

  // make a vector
  let mut v = vec![1,2,3];
  for i in 4..11 {
    v.push(i);
  }
  for (j, l) in v.iter().enumerate() {
    println!("index {}: {}", j, l);
  }
}

Cargo

# New project
cargo new project_name --bin
# Build a release
cargo build --release
# Test a build
cargo check
# Create documentation and open it in a browser
cargo doc --open
# Build the executable, run it
cargo run

rustc

# Build a library
rustc --crate-type=lib thing.rs

Cross-compilation

rustup target list
rustup target add x86_64-unknown-linux-musl
cargo build --target x86_64-unknown-linux-musl

If you’re working on Mac and compiling for Linux, you’ll also want:

brew install x86_64-elf-binutils

And using that specific linker:

[target.x86_64-unknown-linux-musl]
linker = "x86_64-elf-ld"

Nightly rust

# Install nightly toolchain
rustup toolchain install nightly
# Use nightly toolchain by default
rustup default nightly

Resources

Cargo

Cargo watch

cargo watch -x check -x test

Rust for iOS

# Be able to create iOS executables
cargo install cargo-lipo
# Install targets
rustup target add aarch64-apple-ios x86_64-apple-ios

Rust Webassembly

Using –target web

wasm-pack build --target web

<html>
  <head>
    <meta content="text/html;charset=utf-8" http-equiv="Content-Type"/>
  </head>
  <body>
    <!-- Note the usage of `type=module` here as this is an ES6 module -->
    <script type="module">
      // Use ES module import syntax to import functionality from the module
      // that we have compiled.
      //
      // Note that the `default` import is an initialization function which
      // will "boot" the module and make it ready to use. Currently browsers
      // don't support natively imported WebAssembly as an ES module, but
      // eventually the manual initialization won't be required!
      import init, { add } from './pkg/without_a_bundler.js';

      async function run() {
        // First up we need to actually load the wasm file, so we use the
        // default export to inform it where the wasm file is located on the
        // server, and then we wait on the returned promise to wait for the
        // wasm to be loaded.
        //
        // It may look like this: `await init('./pkg/without_a_bundler_bg.wasm');`,
        // but there is also a handy default inside `init` function, which uses
        // `import.meta` to locate the wasm file relatively to js file.
        //
        // Note that instead of a string you can also pass in any of the
        // following things:
        //
        // * `WebAssembly.Module`
        //
        // * `ArrayBuffer`
        //
        // * `Response`
        //
        // * `Promise` which returns any of the above, e.g. `fetch("./path/to/wasm")`
        //
        // This gives you complete control over how the module is loaded
        // and compiled.
        //
        // Also note that the promise, when resolved, yields the wasm module's
        // exports which is the same as importing the `*_bg` module in other
        // modes
        await init();

        // And afterwards we can use all the functionality defined in wasm.
        const result = add(1, 2);
        console.log(`1 + 2 = ${result}`);
        if (result !== 3)
          throw new Error("wasm addition doesn't work!");
      }

      run();
    </script>
  </body>
</html>

Lua

Iterate through file

for line in io.lines("my.txt") do print(line) end

Syntax cheatsheet

function function_name ( args ) body end

while exp do block end

for variable = from_exp , to_exp [, step_exp] do block end
(foreach) for var {, var} in explist do block end

repeat block until exp

if exp then block { elseif exp then block } [ else block ] end

Rexx

https://en.wikipedia.org/wiki/Rexx

JavaScript

Strict Mode

'use strict'

MDN Strict Mode docs

Debugger

debugger;

Classes

Pre-ES5 classes

function Building(x,y,z) {
  this.x = x;
  this.y = y;
  this.z = z;
}

Building.prototype.area = function () {
  return x * y * z;
}

var house = Building(20,20,10);

ES6 Modules

<script type="module">
import * as FOO from './lib/foo.js';
import { baz, bax } from './lib/bar.js';
// ...
</script>

All modules are parsed with strict mode

MDN Modules

var vs. let

Use let, since it limits the scope to the block. const is also block-scoped.

jQuery

https://jquery.com

No-conflict mode

var $j = jQuery.noConflict();

Append a node to the DOM

$('#thing').append('<p>blerg</p>');'</p>')

Get first element of several

CSS pseudo-selectors $(“.stuff li:first”);

DOM traversal $(“.stuff”).first();

Searches for the closest ancestor that matches

.closest()

Objects

Use $(this) instead of this - it’s a jQuery object

Get custom data attributes from the DOM

date(name)

Get direct children from an element

$("ul").children("li");

Get parent element of a node

$("#thing").parent();

Tangle

http://worrydream.com/Tangle/guide.html

CoffeeScript

http://coffeescript.org/ http://www.coffeelint.org/

Typescript

https://www.typescriptlang.org/

React

https://reactjs.org/

React Native

http://facebook.github.io/react-native/ https://reactnative.dev/

jq

d3js

https://d3js.org/