shallow equality

shallowEquality.js

/*eslint-env es6*/

const hasOwn = ({}).hasOwnProperty;

// Check if two objects are equal by comparing own enumerable properties.
const isEqualShallow = (a, b) => {
	if (a === b) return true;
	if (!a || !b) return false;
	const akeys = Object.keys(a);
	const bkeys = Object.keys(b);
	if (akeys.length !== bkeys.length) return false;
	const n = akeys.length;
	while (n--) {
		const k = akeys[n];
		if (!hasOwn.call(b, k) || a[k] !== b[k]) {
			return false;
		}
	}
	return true;
}

// Check if two plain-objects have same properties.
const arePropsEqual = (a, b) => {
	let k, n = 0;
	for (k in a) {
		if (!hasOwn.call(b, k) || a[k] !== b[k]) {
			return false;
		}
		++n;
	}
	for (k in b) --n;
	return !n;
}

// Example of shouldComponentUpdate in React for pure components.
function propsAreChanged(newProps) {
	return !arePropsEqual(this.props, newProps);
}

module.exports = {
	isEqualShallow,
	arePropsEqual,
	propsAreChanged
};