Javascript check if undefined code example
Example 1: js if not undefined
if (typeof myVar !== "undefined") {
console.log("myVar is DEFINED");
}
Example 2: Javascript check if undefined
if (typeof myVariable === 'undefined'){
//myVariable is undefined
}
Example 3: javascript if undefined
if(typeof comment === 'undefined') {
alert('Variable "comment" is undefined.');
} else if(comment === null){
alert('Variable "comment" is null.');
}
Example 4: test if is undefined javascript
let id;
if(typeof id === 'undefined') {
console.log("id is undefined...");
}
Example 5: javascript check if boolean is undefined
if (typeof myFlag !== "undefined") {
// comes here whether myFlag is true or false but not defined
}
Example 6: js check if undefined
let foo = undefined
//will return true
typeof foo === 'undefined'