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Highlighting text in document (JavaScript) Efficiently

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不思量自难忘°
不思量自难忘° 2020-12-20 07:50

How can I (efficiently - not slowing the computer [cpu]) highlight a specific part of a page?

Lets say that my page is as so:
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  • 无人共我
    2020-12-20 08:18 
    <html>
<head>
</head>
<body>
<p id="myText">"My generic words would be selected here" !.</p>
<script>
//highlight code here
var textToHighlight = 'selected here" !';
var text = document.getElementById("myText").innerHTML
document.getElementById("myText").innerHTML = text.replace(textToHighlight, '<span style="color:red">'+textToHighlight+'</span>');
//what sould I write here?
</script>
</body>
</html>
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  • 小蘑菇
    2020-12-20 08:24

    I've adapted the following from my answers to several similar questions on SO (example). It's designed to be reusable and has proved to be so. It traverses the DOM within a container node you specify, searching each text node for the specified text and using DOM methods to split the text node and surround the relevant chunk of text in a styled <span> element.

    Demo: http://jsfiddle.net/HqjZa/

    Code:

    // Reusable generic function
function surroundInElement(el, regex, surrounderCreateFunc) {
    // script and style elements are left alone
    if (!/^(script|style)$/.test(el.tagName)) {
        var child = el.lastChild;
        while (child) {
            if (child.nodeType == 1) {
                surroundInElement(child, regex, surrounderCreateFunc);
            } else if (child.nodeType == 3) {
                surroundMatchingText(child, regex, surrounderCreateFunc);
            }
            child = child.previousSibling;
        }
    }
}

// Reusable generic function
function surroundMatchingText(textNode, regex, surrounderCreateFunc) {
    var parent = textNode.parentNode;
    var result, surroundingNode, matchedTextNode, matchLength, matchedText;
    while ( textNode && (result = regex.exec(textNode.data)) ) {
        matchedTextNode = textNode.splitText(result.index);
        matchedText = result[0];
        matchLength = matchedText.length;
        textNode = (matchedTextNode.length > matchLength) ?
            matchedTextNode.splitText(matchLength) : null;
        surroundingNode = surrounderCreateFunc(matchedTextNode.cloneNode(true));
        parent.insertBefore(surroundingNode, matchedTextNode);
        parent.removeChild(matchedTextNode);
    }
}

// This function does the surrounding for every matched piece of text
// and can be customized  to do what you like
function createSpan(matchedTextNode) {
    var el = document.createElement("span");
    el.style.backgroundColor = "yellow";
    el.appendChild(matchedTextNode);
    return el;
}

// The main function
function wrapText(container, text) {
    surroundInElement(container, new RegExp(text, "g"), createSpan);
}

wrapText(document.body, "selected here");
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  • 独厮守ぢ
    2020-12-20 08:39

    Use this in combination with this and you should be pretty ok. (It is almost better than trying to implement selection / selection-highlighting logic yourself.)

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