javascript test if array code example

Example 1: javascript check if is array

var colors=["red","green","blue"];

if(Array.isArray(colors)){
    //colors is an array
}

Example 2: javascript test if it is an array

// If you want to test if a variable (object) is an instance of 
// an array. You can use the Array.isArray(varName) method
// this method takes one argument, the variable or object you want to test
// and returns true, if the argument is an array 
// or false, if the argument is not an array

if (Array.isArray(object)) {
	// is true
} else {
	// is false
}

Array.isArray([1, 2, 3, 4]); // Returns true
Array.isArray(4); // returns false
// this could be used for flattening an array of arrays

Example 3: js test if array

if(Array.isArray(myVarToTest)) {
	// myVatToTest is an array
} else {
	// myVarToTest is not an array
}

Example 4: how to recognize an array in javascript

const array = [1, 2, 3];

Array.isArray(array);  // => true
Array.isArray(object); // => false
Array.isArray(string); // => false
Array.isArray(empty);  // => false

// other ways

({}).toString.call(array);   // => '[object Array]'
({}).toString.call(object);  // => '[object Object]'
({}).toString.call(string);  // => '[object String]'
({}).toString.call(empty);   // => '[object Null]'

Example 5: javascript check if array is in array

var array = [1, 3],
    prizes = [[1, 3], [1, 4]],
    includes = prizes.some(a => array.every((v, i) => v === a[i]));

console.log(includes);

Example 6: check items in array javascript

function checkAllEven(arr) {
  return arr.every(function(x){
	 return	x % 2 === 0
	})
}

//using "every" to check every item in array.