Question

How I can get a “Some text” from span with id=”old-[id]” and put it in id=”new-[id]” ?

<span id="old-1">Some text</span>
<span id="new-1"></span>
<span id="old-5">Some text</span>
<span id="new-5"></span>

I don’t know how to get a digital part of id without substring() function.
I think exists is more correct solution.
Thanks.

Answer 1

As your question is not entirely clear what you’re asking, I’ll offer you a bunch of different examples:

For a single id, you could do this:

$("#new-1").text($("#old-1").text());

If you have a bunch of sequential IDs that you want to do this on, you could do this:

for (var i = 1; i <= 5; i++) {
    $("#new-" + i).text($("#old-" + i).text());
}

If it’s HTML, not just text, you can use .html() in place of .text() in the above code.

$("#new-1").html($("#old-1").html());

or

for (var i = 1; i <= 5; i++) {
    $("#new-" + i).html($("#old-" + i).html());
}

If you want to find all objects that have IDs that start with “old-” and process all of them regardless of how many and what numbers are on them, you could do this:

$('[id^="old-"]').each(function() {
    var newid = this.id.replace(/old/, "new");
    $("#" + newid).html($(this).html())
})

This will create a jQuery object of all objects that have an id that starts with “old-” and then replace the “old” with “new” to create the destination id value and use that to copy the HTML from the source to the destination.

If you have a given object in a variable named elem and you want to extract just the numeric portion of the id value, you can use a regular expresssion to match the numeric portion like this:

var matches = elem.id.match(/\d+$/);
if (matches) {
    var numString = matches[0];
}