types.js

// Numbers
// Only one number type, 64-bit floating point, no integers
// first class object

// .01024e4
// 2.024e+3
// 10.24E2
// 1024E+1
// 1024.e0
// 1024.e0
// 1024.00
// 1024
// 20140e-1

// Associative Law does not hold

var x = 0.1,
    y = 0.2,
    z = 0.3;

(x + y) + z === x + (y + z);    // false

// Number methods

x.toExponential();
x.toFixed();
x.toLocaleString();
x.toPrecision();
x.toString();
x.valueOf();

// argument Number prototype

if (!Number.prototype.trunc) {
    Number.prototype.trunc = function (number) {
        return Math[number >= 0 ? 'floor' : 'ceiling'](number);
    };
}

// NaN
// Not a Number, result of undefined or erroneous operations
// Toxic, any arithmetic with NaN will have NaN as a result
// Not equal to anything, including itself

NaN === NaN;                    // false
NaN !== NaN;                    // true

// Math object
// Legacy of Java, this should be in the Number.prototype

// methods
Math.abs();
Math.acos();
Math.asin();
Math.atan();
Math.atan2();
Math.ceil();
Math.cos();
Math.exp();
Math.floor();
Math.log();
Math.max();
Math.min();
Math.pow();
Math.random();
Math.round();
Math.sin();
Math.sqrt();
Math.tan();

// Constants
Math.E;
Math.LN10;
Math.LN2;
Math.LOG2E;
Math.LOG10E;
Math.PI;
Math.SQRT1_2;
Math.SQRT2;




// Boolean
true;
false;

// Falsy values, all other values are truthy
false;
null;
undefined;
'';
0;
NaN;






// String

// A sequence of 0 or more characters enclosed with single or double
// quote with \ escapement, no awareness of surrogate pairs
// No separate character type
// Immutable, similar strings are equal( === )

// Convert a number to a string
var str = num.toString();
var str = String(num);

// Convert a string to a number
var num = Number(str);
var num = +str;

// Be aware of the parseInt Radix
parseInt(str, 10);
parseInt("12em");               // 12
parseInt("08");                 // 0
parseInt("08", 10);             // 8

// length property
str.length;

// methods
str.charAt();
str.charCodeAt();
str.concat();
str.indexOf();
str.lastIndexOf();
str.localeCompare();
str.match();
str.replace();
str.search();
str.slice();
str.split();
str.substr();
str.substring();
str.toLocaleLowerCase();
str.toLocaleUpperCase();
str.toLowerCase();
str.toString();
str.toUpperCase();
str.trim();
str.trimLeft();
str.trimRight();
str.valueOf();




// Arrays
// Array inherits from Object, indexes are converted to strings and
// used as names for retrieving values
// Very efficient for sparse arrays, not so efficient in most other cases.

var arr = [1, 2, 3];

// append new items:
arr[arr.length] = 4;

// Do not use for in with arrays, for the order is not guaranteed

for (i = 0; i < arr.length; i += 1) {
    // ...
}

// methods

arr.concat();
arr.every();
arr.filter();
arr.forEach();
arr.indexOf();
arr.join();
arr.lastIndexOf();
arr.map();
arr.pop();
arr.push();
arr.reduce();
arr.reduceRight();
arr.reverse();
arr.shift();
arr.slice();
arr.some();
arr.sort();
arr.splice();
arr.toLocaleString();
arr.toString();
arr.unshift();

// New in ES5
Array.isArray([]);              // true

// notes on sort()
[4, 8, 15, 16, 23, 42].sort();  // [15, 16, 23, 4, 42, 8]

[4, 8, 15, 16, 23, 42].sort(function(x, y) { return x > y; });

// The right way to remove an element
var arr = ['a', 'b', 'c', 'd'];

delete arr[1];                  // ['a', undefined, 'c', 'd']
arr.splice(1, 1);               // ['a', 'c', 'd']




// Date
// Based on Java's Date class

date.now();
date.parse();

date.getDate();
date.getDay();
date.getFullYear();
date.getHours();
date.getMilliseconds();
date.getMinutes();
date.getMonth();
date.getSeconds();
date.getTime();
date.getTimezoneOffset();
date.getUTCDate();
date.getUTCDay();
date.getUTCFullYear();
date.getUTCHours();
date.getUTCMilliseconds();
date.getUTCMinutes();
date.getUTCMonth();
date.getUTCSeconds();
date.getYear();
date.setDate();
date.setFullYear();
date.setHours();
date.setMilliseconds();
date.setMinutes();
date.setMonth();
date.setSeconds();
date.setTime();
date.setUTCDate();
date.setUTCFullYear();
date.setUTCHours();
date.setUTCMilliseconds();
date.setUTCMinutes();
date.setUTCMonth();
date.setUTCSeconds();
date.setYear();
date.toDateString();
date.toGMTString();
date.toISOString();
date.toJSO();
date.toLocaleDateString();
date.toLocaleString();
date.toLocaleTimeString();
date.toString();
date.toTimeString();
date.toUTCString();
date.valueOf();


// RegExp




// All values are objects, except null and undefined

null;                           // a value that isn't anything

undefined;                      // default values for variables and
                                // parameters, also the value of
                                // missing members in objects

typeof object;                  // 'object'
typeof func;                    // 'function'
typeof array;                   // 'object'
typeof number;                  // 'number'
typeof string;                  // 'string'
typeof boolean;                 // 'boolean'
typeof null;                    // 'object'
typeof undefined;               // 'undefined'