How to get input from user using JAVASCRIPT and compare it with array if that value is present in array show present if not show not present.

Question

I have been trying this and i have no idea what i am doing , i think it will use for loop but i dont know how to use it

    <script LANGUAGE="javascript">
    function check(a)
    {
        if(a===list[a])
    {
    document.write("Number is Present");

    }else{
    document.write("Number is not Present");
    }
    }
    </script>
    <script LANGUAGE="javascript">
    var list=[10, 20, 30, 40, 50, 60, 70, 80, 90, 100];
    var n = prompt("Enter any Number");
    check(n);
    console.log(list);
    </script>

What do you think `list[a]` means? You should learn the basics of Javascript and arrays. Look at the `includes()` method, but beware of the difference between numbers and strings. — SLaks, May 07 '18 at 17:16
Re the dupetarget: Although it's asking about an "object," really it's just asking about a value (an object *reference*) in an array. Your numbers are also just values in an array, so the answers there answer this question, too. (SO's definition of a "duplicate.") See those answers for details. — T.J. Crowder, May 07 '18 at 17:31

Sanxofon · Accepted Answer · 2018-05-07T17:39:34.947

1

Here you have. You should learn some javacript. Code.org is a fun place to start

// Define your list before the function
var list=[10, 20, 30, 40, 50, 60, 70, 80, 90, 100];
function check(a) {
  a = parseInt(a); // Convert your user input string to integer
  if(list.indexOf(a)>-1) { // Check if value exists in list
    document.write("Number is Present");
  }else{
    document.write("Number is not Present");
  }
}
// Prompt user for data
var n = prompt("Enter any Number");
check(n);
console.log(list);

edited May 07 '18 at 17:39

answered May 07 '18 at 17:22

Sanxofon

759
9
20

Thankyou so much for your reply. if(list.indexOf(a)>0) change it to if(list.indexOf(a)>-1) then it works properly. – Aashir Irshad May 07 '18 at 17:31
You are right! I've edited the answer. – Sanxofon May 07 '18 at 17:40

score 1 · Answer 2 · answered May 07 '18 at 17:23

function check(a) {
  if (list.indexOf(a) > -1) {
    document.write("Number is Present");
  } else {
    document.write("Number is not Present");
  }
}

var list = [10, 20, 30, 40, 50, 60, 70, 80, 90, 100];
var n = prompt("Enter any Number");
check(n);
console.log(list);

The problem with your code is that the parameter 'a' that you are sending to the check function, is the value you entered. But when you check

if(a===list[a])

the list[a] is the number with the index 'a'.

For example, if i pressed 3, then list[3] would mean 40. (since arrays start from 0)

That doesn't work... the number gets passed as a `String` – Asons May 07 '18 at 17:33 — Asons, May 07 '18 at 17:33

score 0 · Answer 3 · answered May 07 '18 at 17:17

0

Try indexOf

function check(a)
{
    if(list.indexOf(a) > -1)
    {
        document.write("Number is Present");  
    }
    else{
        document.write("Number is not Present");
    }
}

answered May 07 '18 at 17:17

Ashish Ranjan

12,760
5
27
51

score 0 · Answer 4 · answered May 07 '18 at 17:25

What you're doing is just comparing a with the array value present at that index in the array. For example if user types a= 10 then a==list[a] means check if list[10] equals to 10 that means if value in list array at index 10 is equal to the typed value. And of course you'll get undefined many times if user typed a big number.

What you are looking for is .indexOf. This will return you the indexif element is in the array or -1 otherwise.

var list = [1,2,3,4,5,6,7,8,9,10,11,12,14]
var n = prompt("type a number");

console.log(typeof n);

n = parseInt(n);

list.indexOf(n) > -1 ? console.log('In there') : console.log('Not there');

Moreover, you've array of integers and anything you type in prompt will be converted to string. Check console.log(typeof n);. So you'll have to parse it into int to check for your array elements.

How to get input from user using JAVASCRIPT and compare it with array if that value is present in array show present if not show not present.

4 Answers4