check array has element javascript code example

Example 1: js check if array

Array.isArray([1, 2, 3]);	// true
Array.isArray('asdf');		// false

Example 2: javascript check if in array

var extensions = ["image/jpeg","image/png","image/gif"];          
if(extensions.indexOf("myfiletype") === -1){
	alert("Image must be .png, .jpg or .gif");
}