Search Javascript array elements

Question

I would like to create a input that receives a value informed by the user and that when clicking on a button he executed a function that checks if the value entered exists in my array and if there is what index is contained.

var vetor = [1, 2, 3];<br>
var elemento = document.getElementById("verifica").value;

<.input type='text' id="verifica">

Answer 1

You can do it this way: The method indexOf seeks the value (val) in the vector (vetor) if found it returns the position of the element in the array. If it does not find the value it returns -1. An array starts at position 0. I made a sum in the result to increase the positions in a house. So the positions will be greater than zero. It is important to observe the function parseInt() it transforms into integer what is passed as parameter. Which is useful in this example because we want to perform comparisons and operations between integers.

var verifica = function(){
    var vetor = [1, 2, 3];
    var val = document.getElementById("verifica").value;
   
    var a = vetor.indexOf(parseInt(val));

    if(a === -1){

      alert("Valor não encontrado")

    }else if(a !== -1){

      alert("Valor encontrado na posição " + (a+1));

    }

  }

 <input id="verifica" type="text" >
  <button type="submit" onclick="verifica()">Verificar
  </button>

Answer 2

Use a loop to iterate the array elements and if any value matches the input value return the index of that element.

    var vetor = [1, 2, 3, 4, 5];

    function checar(){
      valInput=document.getElementById("verifica").value;
      for (var i = 0; i < vetor.length; ++i) {
          if (vetor[i] == valInput) {
              index = i;
              console.log(index);
              break;
          }
      }
    }

    <input id="verifica" type="text">
    <button type="submit" onclick="checar()">Verificar</button>

Can use findIndex(), but does not work on IE 11 and above