html-ellipsis/out/lib/html-ellipsis.js

truncates a html string without messing up the tags

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.htmlEllipsis = htmlEllipsis;
const tags_1 = require("./tags");
/**
 * Truncates a string to maxLength chars without destroying HTML tags.
 * Optionally adds ellipsis to the end of the string (this does not make
 * the string longer than `maxLength`)
 *
 * @param html - The HTML string to truncate. The function assumes valid HTML.
 * @param maxLength - The max truncated length
 * @param addEllipsis - Add … at the end of the string.
 * @returns The shortened string
 */
function htmlEllipsis(html, maxLength, addEllipsis = false) {
    const len = html.length;
    if (len <= maxLength) {
        return html;
    }
    // leave room for ellipsis
    if (addEllipsis) {
        --maxLength;
    }
    let i = 0;
    let charCount = 0;
    const tagStack = [];
    while (i < len && charCount < maxLength) {
        const char = html.charAt(i);
        const charCode = html.charCodeAt(i);
        if (char === '<') {
            const tag = (0, tags_1.extractTag)(html, i);
            // skip content between < and >
            i += tag.length;
            if ((0, tags_1.isEndTag)(tag)) {
                tagStack.pop();
            }
            else {
                const tagName = (0, tags_1.extractTagName)(tag);
                if (!(0, tags_1.isVoidTag)(tagName)) {
                    tagStack.push(tagName);
                }
            }
        }
        else {
            // if charCode is a high surrogate and if the string contains a
            // low surrogate then count the pair as a single character
            if (charCode >= 0xD800 && charCode <= 0xDBFF && i + 1 < len) {
                ++i;
            }
            ++charCount;
            ++i;
        }
    }
    let result = html.slice(0, i);
    for (let j = tagStack.length - 1; j >= 0; --j) {
        result += '</' + tagStack[j] + '>';
    }
    if (addEllipsis && result.length < html.length) {
        result += '&hellip;';
    }
    return result;
}
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