Variables
To define a variable in PHP, you’d write:
// PHP
$n = 1;
The equivalent in JavaScript is:
// JavaScript
var n = 1;
// PHP
$n = 1;
The equivalent in JavaScript is:
// JavaScript
var n = 1;
There’s no dollar sign, just the name of the variable.
types because the type is derived from the value.
You use varfor all types.
If you need a numeric type, you give your variable a
numeric value. The same applies
to booleans and strings:
var n = 1; // number
var b = true; // boolean
var s = "hello"; // string
You have the option of declaring a variable without
initializing it with a value. In such cases, the variable
is assigned the special value undefined:
var a;
a; // `a` has the special value `undefined`
Redeclaring an existing variable doesn’t set the variable
value back to undefined:
var a = 1;
var a;
// `a` is still 1
You can declare and optionally initialize with a
value several variables with one var statement as
long as you separate them with a comma and
end with a semicolon:
var pi = 3.14,
yeps = true,
nopes,
hi = "hello",
wrrrld = "world";
Technically, var is optional. But unless the variable
was defined higher up in the scope chain , if youskip
var, you end up with a global variable.
And you’ve learned, prob‐ably the hard way, that
global namespace pollution is a sin. Additionally,
there are some subtle differences if you declare
a global variable with and without var.
To cut a long story short, resist this temptation and
always use varto declare your variables.
