Function inputPreviewCallback

lib/internal/repl/utils.js:398–465

(error, inspected)

    }

    const inputPreviewCallback = (error, inspected) => {
      if (inspected == null) {
        return;
      }

      wrapped = false;

      // Ignore the output if the value is identical to the current line.
      if (line === inspected) {
        return;
      }

      if (error) {
        debug('Error while generating preview', error);
        return;
      }
      // Do not preview `undefined` if colors are deactivated or explicitly
      // requested.
      if (inspected === 'undefined' &&
          (!repl.useColors || repl.ignoreUndefined)) {
        return;
      }

      inputPreview = inspected;

      // Limit the output to maximum 250 characters. Otherwise it becomes a)
      // difficult to read and b) non terminal REPLs would visualize the whole
      // output.
      let maxColumns = MathMin(repl.columns, 250);

      // Support unicode characters of width other than one by checking the
      // actual width.
      if (inspected.length * 2 >= maxColumns &&
          getStringWidth(inspected) > maxColumns) {
        maxColumns -= 4 + (repl.useColors ? 0 : 3);
        let res = '';
        for (const char of new SafeStringIterator(inspected)) {
          maxColumns -= getStringWidth(char);
          if (maxColumns < 0)
            break;
          res += char;
        }
        inspected = `${res}...`;
      }

      // Line breaks are very rare and probably only occur in case of error
      // messages with line breaks.
      const lineBreakMatch = RegExpPrototypeExec(/[\r\n\v]/, inspected);
      if (lineBreakMatch !== null) {
        inspected = `${StringPrototypeSlice(inspected, 0, lineBreakMatch.index)}`;
      }

      const result = repl.useColors ?
        `\u001b[90m${inspected}\u001b[39m` :
        `// ${inspected}`;

      const { cursorPos, displayPos } = getPreviewPos();
      const rows = displayPos.rows - cursorPos.rows;