Incrementing Array Index on button click in Javascript

Question

Below is my javascript code! I'm trying to increment the index of array $arr everytime the user clicks a button. The array is defined in a separate php tag! Where am I going wrong?

function option1() {
var i = 0;

document.getElementById("btn0").value = "newButtonValue";
document.getElementById("question").innerHTML = 
"<?php echo $arr["results"][i++]["question"] ?>"; 
}

Where am I going wrong? var i=0 is inside option1 and it is initialized to 0 every time option1 is invoked. — gurvinder372
– gurvinder372, Commented Jan 1, 2018 at 13:03
here <?php echo $arr["results"][i++]["question"] ?> you are mixing an Array in the backend with an index in the frontend. The two are executed (and therefore available) at different times and on different computers. — Thomas
– Thomas, Commented Jan 1, 2018 at 13:06
@Thomas if I add an integer instead of i++ the code runs fine!! It just wont take a variable in the square brackets i.e in [i++] or even [i] — Zaid Waseem
– Zaid Waseem, Commented Jan 1, 2018 at 13:11
@ZaidWaseem because with the static integer, this is all php code now and runs solely in the backend. — Thomas
– Thomas, Commented Jan 1, 2018 at 13:18

ramin ashrafimanesh · Accepted Answer · 2018-01-01 13:09:02Z

1

Where your compiler return output to browser your php code was compiled and you can't run it such as javascript.

you can use this js:

var arr  = <?php echo json_encode($arr["results"]);?>;

function option1() {
    var i = 0;

    document.getElementById("btn0").value = "newButtonValue";
    document.getElementById("question").innerHTML = arr[i++]["question"];
}

answered Jan 1, 2018 at 13:09

ramin ashrafimanesh

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2 Comments

Thomas Over a year ago

I'd extract the var i=0; out of the function, or the i++ is pointless

ramin ashrafimanesh Over a year ago

That's right. check arr[i++] index for undefined bug too.

Milan Akabari · Accepted Answer · 2018-01-01 13:24:43Z

0

.html file

<button onclick="addIndex(this)" queNo="0">newButtonValue</button>

in .js file

function addIndex(btn) {
    var i = btn.getAttribute("queNo")
    console.log(i);
    btn.setAttribute("queNo", i++);

    document.getElementById("question").innerHTML = "<?php echo $arr['results']["+i+"]['question'] ?>"; 
}

Hope it's help you

answered Jan 1, 2018 at 13:24

Milan Akabari

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