JavaScript issue: cant understand why my code doesnt work

Question

Im new to js and I have an issue,

This code works perfectly fine:

function test(args){

    return "12345 - "+args;
}

console.log(test("678910"));

But this code doesn't:

function test(args){
    if(args = ""){
    
    }
    return "12345 - "+args;
}
console.log(test("678910"));

[args] becomes undefined for some reason and I cant understand why, I suppose it has something to do with context, but I still dont understand why nothing works, help would be really appreciated!

`if(args = ""){` you're assigning `args` to an empty string here. You need to use `==` or `===` for comparison — Nick Parsons, Sep 03 '20 at 14:36
Why args becomes undefined after this code is main thing that bothers me — Fedya, Sep 03 '20 at 14:37
When I run your code `args` does **not** become undefined, it gets set to an empty string, which is due to your if-statement (`args = ""`) — Nick Parsons, Sep 03 '20 at 14:37
Does this answer your question? [What is the correct way to check for string equality in JavaScript?](https://stackoverflow.com/questions/3586775/what-is-the-correct-way-to-check-for-string-equality-in-javascript) — Clint, Sep 03 '20 at 14:41
I knew the difference between == and =, i just didnt notice my mistake, thanks to you all again — Fedya, Sep 03 '20 at 14:43

score 2 · Accepted Answer · answered Sep 03 '20 at 14:36

2

The comparison operator is ==, not =. args = "" is assigning args to an empty string, not comparing it. So you should use:

if(args == ""){

answered Sep 03 '20 at 14:36

Anis R.

6,656
2
15
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score 1 · Answer 2 · answered Sep 03 '20 at 14:41

you have to use == in the if statement and also you have to make it do something if args == ""

if (args == "") {
    // Write something to do here.
}

if you don't want it to do anything whe it equals to "", use:

if (args != null) {
   return "12345 - "+args;
}

score 1 · Answer 3 · answered Sep 03 '20 at 14:43

You need to replace = with == in your if Statement: Otherwise you are assigning an empty string to your args parameter.

function test(args){
    if(args == ""){
    
    }
    return "12345 - "+args;
}
console.log(test("678910"));

Also your if doesn't do anything so the return will aways be "12345 - "+args;

If you only want to return, in case args is set do something like this:

if (args) {
    return "12345 - "+args;
}

Pilatos · Answer 4 · 2020-09-03T14:45:00.667

0

This should work just fine ;)

   function test(args){
    if(args == ""){
    
    }
    return "12345 - "+args; }
    console.log(test("678910"));

Or you can use

    function test(args){
      if(args != null){
        return "12345 - "+args;
      }
    }
    console.log(test("678910"));

edited Sep 03 '20 at 14:45

answered Sep 03 '20 at 14:39

Pilatos

21
7

JavaScript issue: cant understand why my code doesnt work

4 Answers4