Page 191 - JavaScript

Will return true if the operands aren't equal.
The javascript engine will try and convert both operands to matching types if they aren't of the
same type. Note: if the two operands have different internal references in memory, then false will
be returned.

Sample:

1 != '1' // false
1 != 2 // true

In the sample above, 1 != '1' is false because, a primitive number type is being compared to a
char value. Therefore, the Javascript engine doesn't care about the datatype of the R.H.S value.

Operator: !== is the inverse of the === operator. Will return true if the operands are not equal or if
their types do not match.

Example:

1 !== '1' // true
1 !== 2 // true
1 !== 1 // false

Logic Operators with Non-boolean values (boolean coercion)

Logical OR (||), reading left to right, will evaluate to the first truthy value. If no truthy value is
found, the last value is returned.

var a = 'hello' || ''; // a = 'hello'
var b = '' || []; // b = []
var c = '' || undefined; // c = undefined
var d = 1 || 5; // d = 1
var e = 0 || {}; // e = {}
var f = 0 || '' || 5; // f = 5
var g = '' || 'yay' || 'boo'; // g = 'yay'

Logical AND (&&), reading left to right, will evaluate to the first falsy value. If no falsey value is
found, the last value is returned.

var a = 'hello' && ''; // a = ''
var b = '' && []; // b = ''
var c = undefined && 0; // c = undefined
var d = 1 && 5; // d = 5
var e = 0 && {}; // e = 0
var f = 'hi' && [] && 'done'; // f = 'done'
var g = 'bye' && undefined && 'adios'; // g = undefined

This trick can be used, for example, to set a default value to a function argument (prior to ES6).

var foo = function(val) {
// if val evaluates to falsey, 'default' will be returned instead.
return val || 'default';

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