How do I use innerHTML inside a loop using JavaScript?

Question

Here is the code and snippet:

var amount = prompt("How many list items would you like?");

if(isNaN(amount) || amount < 1) {
    alert("Please enter a positive whole number");
} else {
    for(i = 0; i <= amount; i++) {
        document.getElementById("content").innerHTML = "Loop: " + i + "<br>"; 
    }
}

<div id="content"></div>

Hi, I'm a new to Javascript and I can't figure this out. How can I write into the div tag "content" using the loop to display values inside the div tag per loop?

The innerHTML is being updated. What is your expected output? — Davin Tryon
– Davin Tryon, Commented Feb 1, 2015 at 22:58

display name · Accepted Answer · 2015-02-01 22:58:54Z

1

Change to += instead of = and start the for loop with 1 unless you want to print out as loop 0, loop 1 and so on...

document.getElementById("content").innerHTML += "Loop: " + i + "<br>";

var amount = prompt("How many list items would you like?");

if(isNaN(amount) || amount < 1) {
    alert("Please enter a positive whole number");
} else {
    for(i = 1; i <= amount; i++) {
        document.getElementById("content").innerHTML += "Loop: " + i + "<br>"; 
    }
}

<div id="content"></div>

answered Feb 1, 2015 at 22:58

display name

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Comments

DrC · Accepted Answer · 2015-02-01 23:04:59Z

Your code looks basically correct but you need to understand the context in which a browser executes javascript. For a given computation (event), the browser usually executes all of that computation before it does any redraws of the actual page. What this means in your case is that only the last value of innerHTML will be used. One approach to this is to accumulate the entire innerHTML value before returning (I see IsabelHM just posted that). The second would be to use something like setTimeout to spread the computation out over multiple "sessions" - something like

var i = 0;
count = function() {
     document.getElementById("content").innerHTML = "Loop: " + i + "<br>";
     i++;
     if (i < amount) {
        window.setTimeout(count, 100);
     }
};
count();

Note - I haven't run that but the idea is there. I basically count at 100ms intervals.

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