Text scrambler effect

textscramble.js

// Scrambled text effect from cultura.xyz
// Can be looped, applied to other elements

class TextScramble {
  constructor(el) {
    this.el = el;
    this.chars = "!<>-_\\/[]{}—=+*^?#________";
    this.update = this.update.bind(this);
  }

  setText(newText) {
    const oldText = this.el.innerText;
    this.el.style.minHeight = `${this.el.offsetHeight}px`; // Preserve height
    this.el.style.display = "inline-block"; // Prevent layout shift
    const length = Math.max(oldText.length, newText.length);
    const promise = new Promise((resolve) => (this.resolve = resolve));
    this.queue = [];
    for (let i = 0; i < length; i++) {
      const from = oldText[i] || "";
      const to = newText[i] || "";
      const start = Math.floor(Math.random() * 40); // Increase randomness start
      const end = start + Math.floor(Math.random() * 40); // Increase duration
      this.queue.push({ from, to, start, end });
    }
    cancelAnimationFrame(this.frameRequest);
    this.frame = 0;
    this.update();
    return promise;
  }

  update() {
    let output = "";
    let complete = 0;
    for (let i = 0, n = this.queue.length; i < n; i++) {
      let { from, to, start, end, char } = this.queue[i];
      if (this.frame >= end) {
        complete++;
        output += to;
      } else if (this.frame >= start) {
        if (!char || Math.random() < 0.28) {
          char = this.randomChar();
          this.queue[i].char = char;
        }
        output += `<span style=\"opacity: 0.7; display: inline-block; width: 1ch;\">${char}</span>`; // Keep space reserved
      } else {
        output += `<span style=\"display: inline-block; width: 1ch;\">${from}</span>`;
      }
    }
    this.el.innerHTML = output;
    if (complete === this.queue.length) {
      this.resolve();
    } else {
      this.frameRequest = requestAnimationFrame(this.update);
      this.frame++;
    }
  }

  randomChar() {
    return this.chars[Math.floor(Math.random() * this.chars.length)];
  }
}

function initTextScrambleForHeaders() {
  const headers = document.querySelectorAll("em");
  const observer = new IntersectionObserver(entries => {
    entries.forEach(entry => {
      if (entry.isIntersecting) {
        const header = entry.target;
        const text = header.innerText;
        const fx = new TextScramble(header);
        fx.setText(text);
        observer.unobserve(header);
      }
    });
  }, { threshold: 0.5 });

  headers.forEach(header => observer.observe(header));
}

document.addEventListener("DOMContentLoaded", () => {
  initTextScrambleForHeaders();
});