javascript undefined null code example

Example 1: null undefined javascript

Undefined  used for unintentionally missing values.

Null       used for intentionally missing values.

Example 2: javascript check for null variables

var myVar=null;

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

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

Example 3: javascript check undefined or null

var myVar=null;

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

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