normalize delta

normalize.js

function eachHardLine(delta, fn) {
  let buffer = new Delta();
  new Delta(delta).eachLine((line, attributes) => {
    buffer = buffer.concat(line);
    if (attributes.br) {
      buffer.insert('\n', attributes);
    } else {
      fn(buffer, attributes);
      buffer = new Delta();
    }
  });
  if (buffer.length > 0) {
    fn(buffer, {});
  }
}

// ensure all these constraints:
// - objects are isolated on their own line
// - empty attributes objects are omitted
// - adjacent string ops with the same attributes are merged
function normalize(delta) {
  const result = new Delta();

  eachHardLine(delta, (line, attributes) => {
    let objectWasLast = false;
    for (let [index, op] of line.ops.entries()) {
      if (typeof op.insert === 'string') {
        // objects must be the last op of the line,
        // insert a line break to make it so
        if (objectWasLast) result.insert('\n', attributes);
        objectWasLast = false;
      } else {
        // objects must be the first op of the line,
        // insert a line break to make it so
        if (index > 0) result.insert('\n', attributes);
        objectWasLast = true;
      }
      // use Delta#insert() to ensure that empty attributes are omitted
      // and that adjacent string ops with the same attributes are merged
      result.insert(op.insert, op.attributes);
    }
    // re-insert the original line break
    result.insert('\n', attributes);
  });

  return result;
};