JavaScript - check length value

Question

I would like to create a form, in this form I have to validate if the value is long enough.... More than 1 character.

My actual code looks like that:

function validateForm(){
    alert("Form ok");
    if(document.getElementsByName("firstname").value.length >1){
        alert("if");
    }
    else{
     document.getElementById("nameValidation").innerHTML= "* You must enter a first name";
        alert("else");
    }

I am struggling to understand why it doesn't work....

Many thanks.

[`document.getElementsByName`](https://developer.mozilla.org/en-US/docs/Web/API/Document/getElementsByName) returns a list of elements — Andreas, Jan 09 '16 at 18:16

score 1 · Answer 1 · answered Jan 09 '16 at 18:16

1

getElementsByName returns array (or array-like object) of elements. You can access each element by index, e.g.:

document.getElementsByName("firstname")[0].value.length

answered Jan 09 '16 at 18:16

madox2

49,493
17
99
99

score 1 · Accepted Answer · answered Jan 09 '16 at 18:18

1

You're using document.getElementsByName which returns NodeList. So, you should use it like this:

document.getElementsByName("firstname")[0].value.length > 1

answered Jan 09 '16 at 18:18

Alexander Ivantsov

294
2
4

Ok, works perfectly now! So this [0] refers to what? – Jullian-luc Barber Jan 09 '16 at 18:20
[0] refers to element at 0th index.. accept the answer if it solves your problem. – Sachin Jan 09 '16 at 18:22
`document.getElementsByName("firstname")[0]` will return a first DOM element with name="firstname". It makes sense because you can have more than one element with the same `name` attribute. – Alexander Ivantsov Jan 09 '16 at 18:23

JavaScript - check length value

2 Answers2