javascript how to ignore if variable is undifined code example

Example 1: js if not undefined

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

Example 2: javascript check if boolean is undefined

if (typeof myFlag !== "undefined") {
  // comes here whether myFlag is true or false but not defined
}

Example 3: undefined javascript check

if(undefinedElement === null) {
	console.log("Element is undefined");
}