For loop - syntax error

Question

I've been staring at this for half an hour and can't find my error. I just have to make a simple for loop that can print something onto the console.

for(var i=0;i<4;i+1){
 console.log(i);
}

It also is asking for a while loop and a do/while loop. I haven't done those yet, but I don't think that's the error. It says: SyntaxError: Unexpected token ILLEGAL

• Steve Wellens: Or the more ubiquitous: i++
• user: i + 1 would not change the value of i after the steps
• Volune: Suggestion for next times: using browser's debugger may help you find the errors.
• nnnnnn: The code shown does not contain a syntax error. It will, however, result in an endless loop because the i variable is set to 0 and then never changed. The "Unexpected token ILLEGAL" error you quote doesn't make sense for the code shown - do you have more code that is not shown?
• Felix Kling: I suggest to learn how to debug JavaScript :)

Answer 1

Your syntax is incorrect. You have to add the 1 to the i, which you are not currently doing.

for(var i=0; i<4; i+=1){
 console.log(i);
}

The classic way, of course is to just do, but I think the first one is more elegant and passes JSLint (which is, of course, the only right way to write javascript).

for(var i=0; i<4; i++){
 console.log(i);
}

If you want your loop to fully pass JSLint, you can do as follows:

var i; // at the top of your function
// ...
for (i = 0; i < 4; i += 1) {
 console.log(i);
}

• nnnnnn: "and passes JSLint" - Does putting var inside the for pass JSLint?
• Jorge Silva: No, it doesn't. I was just referring to the i += 1. When I write a loop, I put the var i outside the loop.
• Felix Kling: Technically the syntax is correct but the logic is incorrect. "which is, of course, the only right way to write javascript" That's very opinionated, isn't it? ;)
• Jorge Silva: No! I'm being completely objective! :). What do you mean by the logic being incorrect, I'd love to correct my answer.
• Felix Kling: I mean that if the syntax was incorrect, the engine would actually throw a syntax error. i+1 is valid syntax, but it doesn't do what the OP intends to do (increment i), thus it's a logic error. I can also be very pedantic so feel free to ignore me ;)

Answer 2

or how 'bout:

for(var i = 0; i < 4; )
 console.log(i++);

Answer 3

I have run your code in Chrome console, and I think your code have no SyntaxError, but it will cause en endless loop.

If you want to run a four loop, you'd better change the code like this:

for(var i=0; i<4; i+=1){
 console.log(i);
}