Question 259725 in Html Question posted in
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Html – How to I create a for-loop that runs through an array?

I am trying to make a function that has a for-loop that goes through the array and should write the number 30 on a new document. But, when I call this function nothing happens, but if I remove the ".length" the document writes the number 10. I’m not sure if the problem is in the for loop or the document.write() function

The document.write() is a placeholder im just using that to make sure the code above it is working correctly.

function TryCode() {



  var codelist = [
  ["test1", 10],
  ["test2", 20],
  ["test3", 30],
];


  for (var i = 0; i < codelist.length;) {
    i++
  }


  document.write(codelist[i][1])

}

I tried running it as it is and nothing happend, it didn’t write anything. But when I remove the length it wrote 10. I understand why it would come out as 10 but I don’t understand why adding the .length makes it not work.

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2

Answers


  1. 0

    Your code has error in for loop it doesn’t correctly iterate through the array, resulting in an attempt to access an invalid index.

    Try this:

    function TryCode() {
    var codelist = [
        ["test1", 10],
        ["test2", 20],
        ["test3", 30],
    ];

    for (var i = 0; i < codelist.length; i++) {
        if (codelist[i][1] === 30) {
            document.write(codelist[i][1]);
        }
    }
}

TryCode();

    In the code I provided the for loop goes through each item in the "codelist" array. If it finds an item where the second part is 30, it writes that number to the document.

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  2. 0

    No need to use a for loop here. Simply use forEach which iterates through every element by itself:

    function TryCode() {
  let codelist = [
    ["test1", 10],
    ["test2", 20],
    ["test3", 30],
  ];

  codelist.forEach(element => {
    document.write(element[1]);
  }); 
}

TryCode();
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