I had an error when I passing a string argument to a function?

Question

I'm sorry. I don't know how to describe this problem carefully.so I hope put my code first.

var test = 'less';
function test_I(tite) {
    console.log(tite);
}
var repeat = "test_I('"+test+"')";
setTimeout(repeat,10);

The code is right, but when I change:
var repeat = "test_I(' "+test+" ')";
to:
var repeat = "test_I("+test+")";,

I get this error in Chrom's console. Why do I need a ' ' When I pass a
String parameter? The error is below.

error

Please don't pass strings to `setTimeout`. Pass a function and arguments, instead: `setTimeout(function, timeout, arg1, arg2, ....)` — Cerbrus, Apr 19 '18 at 14:39

score 0 · Answer 1 · answered Apr 19 '18 at 14:39

Why I need a ' ' When I pass a String parameter

To ensure that less is passed as a String instead of a variable.

If you don't use '', this code var repeat = "test_I("+test+")"; becomes

var repeat = "test_I(less)";

and when setTimeout executes the same it will look for variable less.

score 0 · Answer 2 · answered Apr 19 '18 at 14:39

0

Ah, yes ... interesting fun. If you break down your string to what the JavaScript engine will see, it becomes:

test_I(less)

and less doesn't exist.

if you added "var less='less'" at the beginning of your code, it would then work.

answered Apr 19 '18 at 14:39

theGleep

2 Answers2