Check JSON validation

jsonValidator.js

(function() {
  const text = document.body.textContent; /* define text properly */
  try {
    JSON.parse(text);
    alert("✅ JSON is valid!");
  } catch (error) {
    console.error("❌ Invalid JSON: " + error.message);

    /* Extract position from error message  */
    const match = error.message.match(/position (\d+)/);
    if (match) {
      const pos = parseInt(match[1], 10);

      /* Compute line and column */
      const before = text.substring(0, pos);
      const lines = before.split("\n");
      const lineNumber = lines.length;
      const columnNumber = lines[lines.length - 1].length + 1;

      console.error(`Error at line ${lineNumber}, column ${columnNumber}`);

      /* Show JSON with line numbers and highlight the error line */
      const container = document.createElement("pre");
      container.style.whiteSpace = "pre-wrap";
      container.style.fontFamily = "monospace";

      const allLines = text.split("\n");
      allLines.forEach((line, i) => {
        const div = document.createElement("div");
        div.textContent = (i + 1) + ": " + line;
        if (i + 1 === lineNumber) {
          div.style.background = "yellow"; /* highlight error line */
        }
        container.appendChild(div);
      });

      document.body.innerHTML = ""; /* clear old content */
      document.body.appendChild(container);

      /* Scroll to the highlighted line */
      const highlighted = container.querySelector("div[style*='yellow']");
      if (highlighted) {
        highlighted.scrollIntoView({ behavior: "smooth", block: "center" });
      }
    }
  }
})();

usage.md

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javascript:(function(){const text=document.body.textContent;..........}}}})();