When I run the following piece of code, the firebug console says that elem is undefined, although...it isn't!

var domTools = {};
domTools.searchInElements = function (elem, pattern) {
    if (pattern.constructor !== RegExp) {
        throw "Pattern must be a RegExp";
    }
    if (elem.constructor !== String) {
        throw "Element must be a String";
    }
    elem = document.getElementsByTagName[elem];
    var matches = [];
    for (e = 0; e < elem.length; e++) {
        if (pattern.test(elem[e].innerHTML)) {
            matches.push(elem[e]);
        }
    }
    return matches;
}
domTools.searchInElements("p", /hello/);

It gives me the error during the for statement. All this code is being run whle the page is already loaded. Why is this happening?

When I run the following piece of code, the firebug console says that elem is undefined, although...it isn't!

var domTools = {};
domTools.searchInElements = function (elem, pattern) {
    if (pattern.constructor !== RegExp) {
        throw "Pattern must be a RegExp";
    }
    if (elem.constructor !== String) {
        throw "Element must be a String";
    }
    elem = document.getElementsByTagName[elem];
    var matches = [];
    for (e = 0; e < elem.length; e++) {
        if (pattern.test(elem[e].innerHTML)) {
            matches.push(elem[e]);
        }
    }
    return matches;
}
domTools.searchInElements("p", /hello/);

It gives me the error during the for statement. All this code is being run whle the page is already loaded. Why is this happening?

• javascript
• dom
• element
• getelementsbytagname

Share Improve this question Follow asked Jun 17, 2012 at 0:04 Bobby TablesBobby Tables 1,18444 gold badges1515 silver badges2525 bronze badges

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2 Answers 2

Sorted by: Reset to default 4

It's () and not []

elem = document.getElementsByTagName(elem);

Think of getElementsByTagnName() as a function call so you won't forget that it uses (). And don't forget using the developer console F12 to spot these problems.

As Joseph the Dreamer already found the bug that was causing the error because you've used document.getElementsByTagName[elem]instead ofdocument.getElementsByTagName(elem).

But you may face another problem with this call domTools.searchInElements("p", /hello/); because it'll match hello, helloo, hellos etc so you should use

domTools.searchInElements("p", /^hello$/)

OR just another idea here.