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

2 Answers 2

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.