check if variable is undefined js code example

Example 1: js if not undefined

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

Example 2: javascript check for undefined

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

Example 3: test if is undefined javascript

let id;

if(typeof id === 'undefined') {
    console.log("id is undefined...");
}

Example 4: check if variable is undefined or null jquery

if (variable == null) {
    // variable is either null or undefined
}

Example 5: js check if undefined

let foo = undefined
//will return true
typeof foo === 'undefined'

Example 6: 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).
}