Function canonicalize

src/diff/json.ts:65–127

(
  obj: any,
  stack: Array<any> | null, replacementStack: Array<any> | null,
  replacer: (k: string, v: any) => any,
  key?: string
)

// This function handles the presence of circular references by bailing out when encountering an
// object that is already on the "stack" of items being processed. Accepts an optional replacer
export function canonicalize(
  obj: any,
  stack: Array<any> | null, replacementStack: Array<any> | null,
  replacer: (k: string, v: any) => any,
  key?: string
) {
  stack = stack || [];
  replacementStack = replacementStack || [];

  if (replacer) {
    obj = replacer(key === undefined ? '' : key, obj);
  }

  let i;

  for (i = 0; i < stack.length; i += 1) {
    if (stack[i] === obj) {
      return replacementStack[i];
    }
  }

  let canonicalizedObj: any;

  if ('[object Array]' === Object.prototype.toString.call(obj)) {
    stack.push(obj);
    canonicalizedObj = new Array(obj.length);
    replacementStack.push(canonicalizedObj);
    for (i = 0; i < obj.length; i += 1) {
      canonicalizedObj[i] = canonicalize(obj[i], stack, replacementStack, replacer, String(i));
    }
    stack.pop();
    replacementStack.pop();
    return canonicalizedObj;
  }

  if (obj && obj.toJSON) {
    obj = obj.toJSON();
  }

  if (typeof obj === 'object' && obj !== null) {
    stack.push(obj);
    canonicalizedObj = {};
    replacementStack.push(canonicalizedObj);
    const sortedKeys = [];
    let key;
    for (key in obj) {
      /* istanbul ignore else */
      if (Object.prototype.hasOwnProperty.call(obj, key)) {
        sortedKeys.push(key);
      }
    }
    sortedKeys.sort();
    for (i = 0; i < sortedKeys.length; i += 1) {
      key = sortedKeys[i];
      canonicalizedObj[key] = canonicalize(obj[key], stack, replacementStack, replacer, key);
    }
    stack.pop();
    replacementStack.pop();