有时，遍历DOM以便正确返回字符串

Question

I am testing chrome extension development with a simple content script which traverses the DOM and returns true if a given string is found.

On simple webpages the script returns correctly 100% but on more complex pages eg google search results, it may return true every 1 in 10 times on a page which has the given string.

I am using Crockfords DOM traversal algorithm and have even tried a different algorithm but it gives the same results. I am new to extensions and Javascript and unsure if this is some kind of asynchronous problem?

var exists = false;

function walkTheDOM(node) {
    // String search function 
    if (node.nodeType === 3)
        if (node.nodeValue.indexOf("today") > -1) 
            exists = true;

    // Continue recursive DOM traversal
    node = node.firstChild;
    while (node) {
        walkTheDOM(node);
        node = node.nextSibling;
    }
    return exists;
}

if (walkTheDOM(document.body))
    alert("String exists in page.");

Answer 1

Since pages' content may be dynamic (new content loaded after your code executes), you have 2 possibilities:

1. If you need to have a decision in deterministic time, just wait a bit. Set a timeout from when your script starts executing and check then.

2. If you are okay with changing the decision if a word appears later, your best bet is to run what you're already running, plus set up a listener for DOM changes and analyze the new/modified nodes.

You can combine both methods if your strategy is "detect ASAP, give up in deterministic time".