export function compareProps()

in modules/core/src/lifecycle/props.js [79:130]

• 42 lines of code
• 15 McCabe index (conditional complexity)

export function compareProps({
  newProps,
  oldProps,
  ignoreProps = {},
  propTypes = {},
  triggerName = 'props'
} = {}) {
  // shallow equality => deep equality
  if (oldProps === newProps) {
    return null;
  }

  // TODO - do we need these checks? Should never happen...
  if (typeof newProps !== 'object' || newProps === null) {
    return `${triggerName} changed shallowly`;
  }

  if (typeof oldProps !== 'object' || oldProps === null) {
    return `${triggerName} changed shallowly`;
  }

  // Compare explicitly defined new props against old/default values
  for (const key of Object.keys(newProps)) {
    if (!(key in ignoreProps)) {
      if (!(key in oldProps)) {
        return `${triggerName}.${key} added`;
      }
      const changed = comparePropValues(newProps[key], oldProps[key], propTypes[key]);
      if (changed) {
        return `${triggerName}.${key} ${changed}`;
      }
    }
  }

  // Test if any old props have been dropped
  for (const key of Object.keys(oldProps)) {
    if (!(key in ignoreProps)) {
      if (!(key in newProps)) {
        return `${triggerName}.${key} dropped`;
      }
      if (!Object.hasOwnProperty.call(newProps, key)) {
        // Compare dropped old prop against default value
        const changed = comparePropValues(newProps[key], oldProps[key], propTypes[key]);
        if (changed) {
          return `${triggerName}.${key} ${changed}`;
        }
      }
    }
  }

  return null;
}