3 examples of 'check if value already exists in array javascript' in JavaScript

81
function valueExists(value: any) {
82
    return value != null;
83
}

3
function addToArrayIfNotThere(value, array) {
4
  var i;
5
  for (i = 0; i < array.length; i++) {
6
    if (array[i] === value) {
7
      return i;
8
    }
9
  }
10
  array[i] = value;
11
  return i;
12
}

346
function isExistingAndAdd(search: string, array: string[]) {
347
    if (array.indexOf(search) >= 0) {
348
        array.push(search);
349
        return true;
350
    }
351
    array.push(search);
352
    return false;
353
}