Question about loop in javascript

Question

I tried this loop, but isn't working (Syntax errors). What is the correct way to do it? up+i doesn't work for example.

  for(i=0;i<10;i++) {
            up+i = function() {
                base.refresh("Field"+i, $t+i);
            }
        }

up+i = function() isn't valid Javascript, that's why you get syntax error — Markus Hedlund
– Markus Hedlund, Commented May 16, 2011 at 17:29
@Fel that isn't really going to work. Have you considered using an array instead? e.g.: up[i] = ... — Brian Driscoll
– Brian Driscoll, Commented May 16, 2011 at 17:29
Ah. You can't do up+i, but you can do window['up' + i]. Though I don't recommend it — Markus Hedlund
– Markus Hedlund, Commented May 16, 2011 at 17:30

JaredPar · Accepted Answer · 2011-05-16 17:44:48Z

3

The primary issue is around this line

up+i = function() {

The expression up+i produces a value, not a variable, and a place which can be assigned to. Were you trying instead to assign into an array? If so change it to the following

up[i] = function() {

EDIT

OP clarified that the intent is to create 10 named functions. In that case there needs to be an object to hang them off of. I'll call it root for an example

var root = {};
for (i = 0; i < 10; i++) {
  root['up' + i] = function() { 
    base.refresh("Field"+i, $t+i);
  };
}

Additionally right now the function is capturing a single i meaning all instances of the function will have the same value for i. To prevent this use a separate function to capture the value.

var root = {};
for (i = 0; i < 10; i++) {
  root['up' + i] = function(arg) { 
    return function() { base.refresh("Field"+arg, $t+arg); };
  } (i);
}

edited May 16, 2011 at 17:44

answered May 16, 2011 at 17:31

JaredPar

760k152 gold badges1.3k silver badges1.5k bronze badges

Sign up to request clarification or add additional context in comments.

10 Comments

Nick Berardi Over a year ago

This isn't right, see the second comment for what he was trying to do. He was trying to make 10 functions, not an array of 10 functions.

JaredPar Over a year ago

@Nick, when clarifications to questions are added after the fact it's much better to comment to notify people and then later down vote not immediately

anvd Over a year ago

@jared the comment that i posted to Nick also applies to your suggestion.

JaredPar Over a year ago

@Fel what did you intend for $t to reference? It's hard to help unless we know the intent of that value

anvd Over a year ago

if i use $t+i i get the error, but this. $t0, $t1, $t2 works well. Probably the best choice is separate pieces of code... thanks anyway.

|

Tadeck · Accepted Answer · 2011-05-16 17:34:58Z

1

The code responsible for looping works. Just see here: http://jsfiddle.net/7aZLv/ (warning! opens 10 alert boxes one after another)

EDIT:

You can create global functions like that: http://jsfiddle.net/7aZLv/1/

for(i=0;i<10;i++) {
    window['up'+i] = function(){
        alert('test');
    }
}

up3(); // will make alert appear

The error happened because you assignment expression was incorrect (you assigned value to expression, not a variable how it should be assigned).

edited May 16, 2011 at 17:34

answered May 16, 2011 at 17:29

Tadeck

138k28 gold badges155 silver badges201 bronze badges

Comments

Jimmy · Accepted Answer · 2011-05-16 17:29:03Z

0

Maybe it should just be

for(i=0;i<10;i++) {
        up = function() {
            base.refresh("Field"+i, $t+i);
        }
    }

? We need lots of information to help you, what is up supposed to be, what are you trying to accomplish? What syntax errors are you getting?

answered May 16, 2011 at 17:29

Jimmy

9,83514 gold badges62 silver badges81 bronze badges

1 Comment

Nick Berardi Over a year ago

He wants it to generate up1, up2, up3, up4, etc.

Jeff · Accepted Answer · 2011-05-16 17:29:53Z

0

You cannot have an expression on the left hand side of an assignment. is up+i supposed to be pointer arithmetic? if so, there are no pointers in javascript. i cannot tell what you are trying to do, but the first thing to do would be to change up+i = function() { ...} to up = function() {...} or else get a new variable to assign it too.

answered May 16, 2011 at 17:29

Jeff

14.3k12 gold badges61 silver badges107 bronze badges

Comments

Danzan · Accepted Answer · 2011-05-16 17:30:52Z

0

Many errors in your code.

up is string? $t what is this?

maybe like this?

for(i=0;i<10;i++) {
var new_func = 'up' + i;
        new_func = function() {
            base.refresh("Field"+i, $t+i);
        }
    }

answered May 16, 2011 at 17:30

Danzan

9685 silver badges8 bronze badges

Comments

Craig M · Accepted Answer · 2011-05-16 17:33:05Z

0

Instead of trying to create individual variables for the functions, you can add them to an array.

var ups;

for(i=0;i<10;i++) {
    ups.push(function() {
        base.refresh("Field"+i, $t+i);
    });
}

answered May 16, 2011 at 17:33

Craig M

5,6084 gold badges34 silver badges43 bronze badges

Comments

Nick Berardi · Accepted Answer · 2011-05-16 17:34:13Z

0

try this

for(i=0;i<10;i++) {
   window["up" +i] = function() {
      base.refresh("Field"+i, $t+i);
   }
}

This will add the functions to the window object so that you can make calls like this after it:

up0();
up1();
// etc

answered May 16, 2011 at 17:34

Nick Berardi

55k15 gold badges118 silver badges137 bronze badges

2 Comments

anvd Over a year ago

ReferenceError: $t is not defined. But if i use $t1 directly the error go away.

Nick Berardi Over a year ago

Don't know it is your syntax.

Collectives™ on Stack Overflow

Question about loop in javascript

7 Answers 7

10 Comments

Comments

1 Comment

Comments

Comments

Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

7 Answers 7

10 Comments

Comments

1 Comment

Comments

Comments

Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related