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JavaScript JavaScript Loops, Arrays and Objects Simplify Repetitive Tasks with Loops For Loops

Posted by john larson
john larson
16,594 Points

ReferenceError: Invalid left-hand side in assignment

var html = "";
var i;
for (i = 0; i < 10; 1 += 1) {
  html += "<div>" + i + "</div>";
}
document.getElementById("print").innerHTML = html;
john larson
john larson
16,594 Points

I just can't see what I'm missing

1 Answer

Alec Plummer
Alec Plummer
15,181 Points
Alec Plummer
Alec Plummer
15,181 Points

Your for loop is constructed a little wompy, this should fix your problem. Define i inside of the for loop, you don't want to clutter your global scope with throw away variables. The for loop is broken down into its 3 sections; define counter, check counter against length(in this case, 10), add 1 to i(i++). Then it repeats by checking i against length(10) and adding 1 to i until i is no longer less than length. 

var html = "";
for (var i = 0; i < 10; i++) {
    html+= "div" + i "</div>";
}
john larson
john larson
16,594 Points

Alec, thank you for your response. I'm getting mixed messages on where to declare... var i, in for loop. I know at this point in the course Dave declares it inside (). but js lint and I believe w3schools says to declare it before the loop.

Alec Plummer
Alec Plummer
15,181 Points
Alec Plummer
Alec Plummer
15,181 Points

No problem. It can be confusing when you first start learning, wait until you get to objects and prototypal inheritance for the first time lol. Always declare within the loop, I've never seen var = i; declared outside of the loop in production. The reason being that you don't want to clutter the global scope if you don't have to. You wouldn't want some random variable screwing you up 100+ lines down the js file lol.

john larson
john larson
16,594 Points

Ok, so them I'm thinking that the places I've seen var i; declared outside a loop, it was possibly inside a function. That way it will not muddle up the global scope?

Alec Plummer
Alec Plummer
15,181 Points
Alec Plummer
Alec Plummer
15,181 Points

could be, as a rule of thumb though you always want to declare the counter within the loop. When looking at w3schools, keep in mind that the sample code is just to illustrate something and not necessarily how you would write that code in 'the real world' so to speak.

john larson
john larson
16,594 Points

Wow, that makes a huge difference, cause I got the impression that their stuff was THE way to do it. So, thanks for sharing that with me. There's still the js Lint thing saying to declare var i: outside the loop. But I get the impression that Lint is not all it's cracked up to be either. Thanks again.