How can i compare a variable value from prompt() to all elements of an array

Question

I tried this...

var age = prompt("your age");
var myArray = new Array(1, 2, 3, 4, 5);
if (age == myArray) {
   alert("we know your age");
else {
   alert("new age added");

I want to compare the prompt() value to the list in the array

You want to check it is present in `array`? – Maheer Ali Feb 06 '19 at 16:24 — Maheer Ali, Feb 06 '19 at 16:24

ellipsis · Answer 1 · 2019-02-06T16:27:18.090

1

Use includes method to check if age is already in the array or not. Includes check if a given variable present in the array or not.

var age = prompt("your age");
var myArray = new Array(1, 2, 3, 4, 5);
if (myArray.includes(Number(age))) {
   alert("we know your age");
   }
else {
   alert("new age added");  
   }

You can also use indexOf method to find the index of the variable in the array. If it is not present, it will output -1

var age = prompt("your age");
var myArray = new Array(1, 2, 3, 4, 5);
if (myArray.indexOf(Number(age))!=-1) {
   alert("we know your age");
   }
else {
   alert("new age added");  
   }

edited Feb 06 '19 at 16:27

answered Feb 06 '19 at 16:24

ellipsis

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Just for the sake of adding useful infos, beware of IE, which lacks the support for `Array.prototype.includes`. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/includes#Browser_compatibility – briosheje Feb 06 '19 at 16:27
I worked this way – CirLorm Feb 06 '19 at 16:47

Code Maniac · Accepted Answer · 2019-02-06T16:25:51.447

0

You can use some to iterate through myArray and check if any of the element is same as input given by user.

var age = prompt("your age");
var myArray = new Array(1, 2, 3, 4, 5);
if (myArray.some(e=> e == age)) {
   alert("we know your age");
} else {
   alert("new age added"); 
}

edited Feb 06 '19 at 16:25

answered Feb 06 '19 at 16:24

Code Maniac

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Why not use find here? – Luca Kiebel Feb 06 '19 at 16:25
@LucaKiebel yes you can use. but here in return we want true or false. find returns the matched element that will implicitly changes to true or false. – Code Maniac Feb 06 '19 at 16:27

score 0 · Answer 3 · answered Feb 06 '19 at 16:28

You can use Array.prototype.includes() which Boolean. And you also need to parseInt() age And try to avoid creating Array like this. Use []

var age = parseInt(prompt("your age"));
var myArray = [1, 2, 3, 4, 5];
if (myArray.includes(age)) {
   alert("we know your age");
   }
else {
   alert("new age added"); 
   }

score 0 · Answer 4 · answered Feb 06 '19 at 16:28

If you want to check if the age is included in the array, you can use includes, don't forget to parse the input to a number if it is a string, you can do this with parseInt, Number or by prepending a + in front of the string:

const age = prompt('your age');
const myArray = new Array(1, 2, 3, 4, 5);
if (myArray.includes(Number(age))) {
   alert('we know your age');
} else {
   alert('new age added');
}

How can i compare a variable value from prompt() to all elements of an array

4 Answers4