How do you get and set the caret position in a contenteditable?

问题

This question has some answers here but there's a few problems.

Basically I want to do the following:

1. get caret position
2. set innerHTML of the contenteditable (this resets the caret position)
3. set the caret position to the value obtained in step 1.

A lot of the existing answers seem to be complicated by cross-browser support but I only need it to work on modern chrome. It also needs to work with html. Ideally it would look exactly like this:

var index = getCaretPosition(contentEditableDiv);
onEdit(contentEditableDiv); // <-- callback function that manipulates the text and sets contentEditableDiv.innerHTML = theManipulatedText
setCaretPosition(contentEditableDiv, index);

I've tried looking through the documentation but it's not straightforward and I think this question is due for a leaner answer anyways.

回答1:

This seems to work for me but I've only tested it for my use cases.

GET

function getCaretIndex(win, contentEditable) {
    var index = 0;
    var selection = win.getSelection();
    var textNodes = textNodesUnder(contentEditable);

    for(var i = 0; i < textNodes.length; i++) {
        var node = textNodes[i];
        var isSelectedNode = node === selection.focusNode;

        if(isSelectedNode) {
            index += selection.focusOffset;
            break;
        }
        else {
            index += node.textContent.length;
        }
    }

    return index;
}

SET

function setCaretIndex(win, contentEditable, newCaretIndex) {
    var cumulativeIndex = 0;
    var relativeIndex = 0;
    var targetNode = null;

    var textNodes = textNodesUnder(contentEditable);

    for(var i = 0; i < textNodes.length; i++) {
        var node = textNodes[i];
        
        if(newCaretIndex <= cumulativeIndex + node.textContent.length) {
            targetNode = node;
            relativeIndex = newCaretIndex - cumulativeIndex;
            break;
        }

        cumulativeIndex += node.textContent.length;
    }

    var range = win.document.createRange();
    range.setStart(targetNode, relativeIndex);
    range.setEnd(targetNode, relativeIndex);
    range.collapse();

    var sel = win.getSelection();
    sel.removeAllRanges();
    sel.addRange(range);
}

REQUIRED HELPER

function textNodesUnder(node) { // https://stackoverflow.com/a/10730777/3245937
    var all = [];
    for (node=node.firstChild;node;node=node.nextSibling){
        if (node.nodeType==3) {
            all.push(node);
        }
        else {
            all = all.concat(textNodesUnder(node));
        }
    }
    return all;
}

TEST (just call this function)

It loops through the text in a contenteditable, sets the caret index, then reads it. Console output is: (setIndex | getIndex)

function testContentEditable() {
    document.body.innerHTML = "<div contenteditable></div>"
    var ce = document.querySelector("[contenteditable]");
    ce.focus();
    ce.innerHTML = "HELLO <span data-foo='true' style='text-decoration: underline;'><span style='color:red;'>WORLD</span> MY</span> NAME IS BOB";
    
    var i = 0;
    var intv = setInterval(function() {
        if(i == ce.innerText.length) {
            clearInterval(intv);
        }

        setCaretIndex(window, ce, i);

        var currentIndex = getCaretIndex(window, ce);
        console.log(i + " | " + currentIndex);

        i++;
    }, 100);
}

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FIDDLE

function getCaretIndex(win, contentEditable) {
    var index = 0;
    var selection = win.getSelection();
    var textNodes = textNodesUnder(contentEditable);

    for(var i = 0; i < textNodes.length; i++) {
        var node = textNodes[i];
        var isSelectedNode = node === selection.focusNode;

        if(isSelectedNode) {
            index += selection.focusOffset;
            break;
        }
        else {
            index += node.textContent.length;
        }
    }

    return index;
}

function setCaretIndex(win, contentEditable, newCaretIndex) {
    var cumulativeIndex = 0;
    var relativeIndex = 0;
    var targetNode = null;

    var textNodes = textNodesUnder(contentEditable);

    for(var i = 0; i < textNodes.length; i++) {
        var node = textNodes[i];
        
        if(newCaretIndex <= cumulativeIndex + node.textContent.length) {
            targetNode = node;
            relativeIndex = newCaretIndex - cumulativeIndex;
            break;
        }

        cumulativeIndex += node.textContent.length;
    }

    var range = win.document.createRange();
    range.setStart(targetNode, relativeIndex);
    range.setEnd(targetNode, relativeIndex);
    range.collapse();

    var sel = win.getSelection();
    sel.removeAllRanges();
    sel.addRange(range);
}

function textNodesUnder(node) { // https://stackoverflow.com/a/10730777/3245937
    var all = [];
    for (node=node.firstChild;node;node=node.nextSibling){
        if (node.nodeType==3) {
            all.push(node);
        }
        else {
            all = all.concat(textNodesUnder(node));
        }
    }
    return all;
}

function testContentEditable() {
    document.body.innerHTML = "<div contenteditable></div>"
    var ce = document.querySelector("[contenteditable]");
    ce.focus();
    ce.innerHTML = "HELLO <span data-foo='true' style='text-decoration: underline;'><span style='color:red;'>WORLD</span> MY</span> NAME IS BOB";
    
    var i = 0;
    var intv = setInterval(function() {
        if(i == ce.innerText.length) {
            clearInterval(intv);
        }

        setCaretIndex(window, ce, i);

        var currentIndex = getCaretIndex(window, ce);
        console.log(i + " | " + currentIndex);

        i++;
    }, 100);
}
testContentEditable();

来源：https://stackoverflow.com/questions/64618729/how-do-you-get-and-set-the-caret-position-in-a-contenteditable