is empty in javascript code example

Example 1: is var is not blank then display value in javascript

if(data !== null && data !== '') {
   // do something
}

Example 2: javascript if string empty

// Test whether strValue is empty or is None
if (strValue) {
    //do something
}
// Test wheter strValue is empty, but not None 
if (strValue === "") {
    //do something
}

Example 3: javascript check for null variables

var myVar=null;

if(myVar === null){
    //I am null;
}

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

Example 4: empty string in javascript

var s; // undefined
var s = ""; // ""
s.length // 0

Example 5: empty javascript

'use strict';
delete Object.prototype; // throws a TypeError