javascript if undefined
snippet in javascript

js if not undefined

user377

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

javascript check for undefined

user4162

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

javascript if undefined

user2163

if(typeof comment === 'undefined') {

  alert('Variable "comment" is undefined.');

} else if(comment === null){

  alert('Variable "comment" is null.');

}

javacript detect undefined

user2804

//detecting undefined object property
if (typeof person.last_name === "undefined") {
    console.log("person last_name is undefined");
}

//detecting undefined variable 
if (typeof myVar === "undefined") {
    console.log("myVar is undefined");
}

assign this value or if it is undefined this other value javascript

user350

var x; //variable to change
var y; //higher priority variable
var z = 12; //lower priority variable
x = !(y === undefined) ? y : z;
console.log(x); //12

check if variable is undefined or null jquery

user9984

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