javascript null or undefined code example

Example 1: js if not undefined

if (typeof myVar !== "undefined") {
    console.log("myVar is DEFINED");
}

Example 2: javascript check if undefined or null

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

Example 3: null undefined javascript

Undefined  used for unintentionally missing values.

Null       used for intentionally missing values.

Example 4: javascript check for null variables

var myVar=null;

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

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