javascript library test null undefined code example

Example 1: javascript check if undefined or null

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

Example 2: javascript syntax for check null or undefined or empty

if (typeof value !== 'undefined' && value) {
    //deal with value'
};

Example 3: javascript check if undefined or null

// simple check do the job
if (myVar) {
 // comes here either myVar is not null,
 // or myVar is not undefined,
 // or myVar is not '' (empty string).
}