looking at the source code of immutability-helper , I am confused about one of the functions
update.isEquals = function(a, b) { return a === b; };
function update(object, spec) {
if (typeof spec === "function") {
return spec(object);
}
if (!(Array.isArray(object) && Array.isArray(spec))) {
invariant(
!Array.isArray(spec),
"update(): You provided an invalid spec to update(). The spec may " +
"not contain an array except as the value of $set, $push, $unshift, " +
"$splice or any custom command allowing an array value."
);
}
invariant(
typeof spec === "object" && spec !== null,
"update(): You provided an invalid spec to update(). The spec and " +
"every included key path must be plain objects containing one of the " +
"following commands: %s.",
Object.keys(commands).join(", ")
);
var nextObject = object;
var index, key;
getAllKeys(spec).forEach(function(key) {
if (hasOwnProperty.call(commands, key)) {
var objectWasNextObject = object === nextObject;
nextObject = commands[key](spec[key], nextObject, spec, object);
// update.isEquals(nextObject, object) true nextObject object, nextObject = object
if (objectWasNextObject && update.isEquals(nextObject, object)) {
nextObject = object;
}
} else {
var nextValueForKey =
type(object) === "Map"
? update(object.get(key), spec[key])
: update(object[key], spec[key]);
if (!update.isEquals(nextValueForKey, nextObject[key]) || typeof nextValueForKey === "undefined" && !hasOwnProperty.call(object, key)) {
if (nextObject === object) {
nextObject = copy(object);
}
if (type(nextObject) === "Map") {
nextObject.set(key, nextValueForKey);
} else {
nextObject[key] = nextValueForKey;
}
}
}
})
return nextObject;
} this function? update.isEquals (nextObject, object) means that the two are equal
if (objectWasNextObject && update.isEquals(nextObject, object)) {
nextObject = object;
}