how to check if var is undefined in javascript code example
Example 1: javascript if undefined
if(typeof comment === 'undefined') {
alert('Variable "comment" is undefined.');
} else if(comment === null){
alert('Variable "comment" is null.');
}
Example 2: js check if undefined
let foo = undefined
//will return true
typeof foo === 'undefined'
Example 3: javascript check undefined
if(myVar === null) {
console.log("Element is undefined");
}
Example 4: 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).
}