117 lines
4.1 KiB
JavaScript
117 lines
4.1 KiB
JavaScript
/**
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* A helper function to get the X/Y coordinates of the current cursor position within an element.
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* For a full explanation see the post by Jhey Tompkins: https://medium.com/@jh3y/how-to-where-s-the-caret-getting-the-xy-position-of-the-caret-a24ba372990a
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*
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* @param {element} input The DOM element the cursor is to be found within
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* @param {number} selectionPoint The current cursor position (e.g. either selectionStart or selectionEnd)
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*
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* @returns {object} An object with x and y properties (e.g. {x: 10, y: 0})
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*
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* @example
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* const coordinates = getCursorXY(elementRef.current, elementRef.current.selectionStart)
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*/
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export const getCursorXY = (input, selectionPoint) => {
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const bodyRect = document.body.getBoundingClientRect();
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const elementRect = input.getBoundingClientRect();
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const inputY = elementRect.top - bodyRect.top;
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const inputX = elementRect.left - bodyRect.left;
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// create a dummy element with the computed style of the input
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const div = document.createElement('div');
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const copyStyle = getComputedStyle(input);
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for (const prop of copyStyle) {
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div.style[prop] = copyStyle[prop];
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}
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// set the div to the correct position
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div.style['position'] = 'absolute';
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div.style['top'] = `${inputY}px`;
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div.style['left'] = `${inputX}px`;
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div.style['opacity'] = 0;
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// replace whitespace with '.' when filling the dummy element if it's a single line <input/>
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const swap = '.';
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const inputValue =
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input.tagName === 'INPUT' ? input.value.replace(/ /g, swap) : input.value;
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// set the div content to that of the textarea up until selection point
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div.textContent = inputValue.substr(0, selectionPoint);
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if (input.tagName === 'TEXTAREA') div.style.height = 'auto';
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// if a single line input then the div needs to be single line and not break out like a text area
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if (input.tagName === 'INPUT') div.style.width = 'auto';
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// marker element to obtain caret position
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const span = document.createElement('span');
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// give the span the textContent of remaining content so that the recreated dummy element is as close as possible
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span.textContent = inputValue.substr(selectionPoint) || '.';
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// append the span marker to the div and the dummy element to the body
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div.appendChild(span);
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document.body.appendChild(div);
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// get the marker position, this is the caret position top and left relative to the input
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const { offsetLeft: spanX, offsetTop: spanY } = span;
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// remove dummy element
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document.body.removeChild(div);
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// return object with the x and y of the caret. account for input positioning so that you don't need to wrap the input
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return {
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x: inputX + spanX,
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y: inputY + spanY,
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};
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};
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/**
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* A helper function that searches back to the beginning of the currently typed word (indicated by cursor position) and verifies whether it begins with an '@' symbol for user mention
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*
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* @param {element} textArea The text area or input to inspect the current word of
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* @returns {{isUserMention: boolean, indexOfMentionStart: number}} Object with the word's mention data
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*
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* @example
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* const { isUserMention, indexOfMentionStart } = getMentionWordData(textArea);
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* if (isUserMention) {
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* // Do something
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* }
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*/
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export const getMentionWordData = (textArea) => {
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const { selectionStart, value: valueBeforeKeystroke } = textArea;
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if (selectionStart === 0 || valueBeforeKeystroke === '') {
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return {
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isUserMention: false,
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indexOfMentionStart: -1,
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};
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}
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const indexOfAutocompleteStart = getIndexOfCurrentWordAutocompleteSymbol(
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valueBeforeKeystroke,
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selectionStart,
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);
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return {
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isUserMention: indexOfAutocompleteStart !== -1,
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indexOfMentionStart: indexOfAutocompleteStart,
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};
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};
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const getIndexOfCurrentWordAutocompleteSymbol = (content, selectionIndex) => {
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const currentCharacter = content.charAt(selectionIndex);
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const previousCharacter = content.charAt(selectionIndex - 1);
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if (
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selectionIndex !== 0 &&
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previousCharacter !== ' ' &&
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previousCharacter !== ''
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) {
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return getIndexOfCurrentWordAutocompleteSymbol(content, selectionIndex - 1);
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}
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if (currentCharacter === '@') {
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return selectionIndex;
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}
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return -1;
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};
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