JavaScript


Global Objects

Array
An array is an ordered collection of elements that can be selected by indices. JS Bin
var ballsArray = ["Titleist", "Callaway", "Srixon"];
var scoresArray = [80, 82, 79];
Boolean
A boolean object is an object wrapper around the fundamental boolean datatype value (true or false).
var bool = false;
alert('bool is ' + bool);
Date
A date object is used to work with dates and times. JS Bin
// new Date object
var d = new Date();
d.getFullYear();

// date string
var s = Date();
console.log(s);
Error
An error object contains information to describe JavaScript errors. JS Bin
try {
    throw new Error("Oh Snap");
} catch (e) {
    console.log(e.name + ": " + e.message);
}
JSON
A JSON (JavaScript Object Notation) object is used for converting values to JSON and values from JSON.
var json = '{"result":true,"count":1}',
obj = JSON.parse(json);
console.log(obj.count);
console.log(JSON.stringify(obj));
Math
A math object is used for mathematical functions and constants.
// shows 10
alert(Math.floor(10.6));
Number
A number object is used for numeric functions and constants.
// create number object
var num = new Number(10);
RegExp
A RegExp object is to create regular expressions for pattern matching. JS Bin
// regular expression defining 5 digits
var fiveDigitPattern=/^\d{5}$/;
var digits = "12345";
alert(digits.search(fiveDigitPattern)== -1? false:true );
String
A string object is used for string functions and constants.
// create string object
var str = new String("Hello world");
//or
var str = "Hello world";
Functions & Properties
decodeURI
A function that returns a decoded URI by replacing each UTF-8 escape sequence with it’s respective characters. JS Bin
console.log(decodeURI('~!@#$%25%5E&*()=+%5B%5D%7B%7D%5C;:\'%22,/?'));
decodeURIComponent
A function that returns a decoded URI component by replacing each UTF-8 escape sequence with it’s respective characters. JS Bin
console.log(decodeURIComponent('~!%40%23%24%25%5E%26*()%3D%2B%5B%5D%7B%7D%5C%3B%3A\'%22%2C%2F%3F'));
encodeURI
A function that returns an encoded URI by replacing all special characters with their respective UTF-8 escape sequences. JS Bin
console.log(encodeURI('~!@#$%^&*()=+[]{}\\;:\'",/?'));
encodeURIComponent
A function that returns an encoded URI component by replacing all special characters with their respective UTF-8 escape sequences. JS Bin
console.log(encodeURIComponent('~!@#$%^&*()=+[]{}\\;:\'",/?'));
eval
A function that evaluates a JavaScript expression.
var x = 5;
var str = "if (x == 5) {console.log('z is 42'); z = 42;} else z = 0; ";
eval(str);
infinity
A property that represents a number that is greater than any other number, including itself.
var x = Math.pow(2, 1024);
console.log(x);
    
isFinite
A function that returns true if the value exceeds the lower limit 5e-324 (Number.MIN_VALUE) or the upper limit 1.7976931348623157e+308 (Number.MAX_VALUE), false otherwise.
var x = isFinite(Math.sqrt(-4));
console.log(x);
var y = isFinite(50);
console.log(y);
isNaN
A function that returns true if the value is a number, false otherwise.
console.log(isNaN(50));
console.log(isNaN('foo'));
NaN
A property that represents a NaN (Not a Number) value.
console.log(Number('foo'));
parseFloat
A function that returns the float value of a variable.
// both return 1.505
console.log(parseFloat('1.5050'));
console.log(parseFloat('0.015050E+2'));
parseInt
A function that returns the integer value of a variable.
// return 50
console.log(parseInt('50');
undefined
A property that represents a variable that has not been declared or initialised. JS Bin
foo; // throws an error, foo is not defined
var foo; // foo is uninitialised

if (typeof foo === 'undefined') {
    // foo is undefined
}

Resources

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