element-web/src/ObjectUtils.js
Richard van der Hoff 393e8ff612 Revert "Revert "Merge pull request #193 from matrix-org/rav/shouldComponentUpdates""
Put the shouldComponentUpdate methods back in, now that Matthew has stopped
demoing.

This reverts commit 606fdcb8df.
2016-03-09 15:56:53 +00:00

110 lines
3.8 KiB
JavaScript

/*
Copyright 2016 OpenMarket Ltd
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
/**
* For two objects of the form { key: [val1, val2, val3] }, work out the added/removed
* values. Entirely new keys will result in the entire value array being added.
* @param {Object} before
* @param {Object} after
* @return {Object[]} An array of objects with the form:
* { key: $KEY, val: $VALUE, place: "add|del" }
*/
module.exports.getKeyValueArrayDiffs = function(before, after) {
var results = [];
var delta = {};
Object.keys(before).forEach(function(beforeKey) {
delta[beforeKey] = delta[beforeKey] || 0; // init to 0 initially
delta[beforeKey]--; // keys present in the past have -ve values
});
Object.keys(after).forEach(function(afterKey) {
delta[afterKey] = delta[afterKey] || 0; // init to 0 initially
delta[afterKey]++; // keys present in the future have +ve values
});
Object.keys(delta).forEach(function(muxedKey) {
switch (delta[muxedKey]) {
case 1: // A new key in after
after[muxedKey].forEach(function(afterVal) {
results.push({ place: "add", key: muxedKey, val: afterVal });
});
break;
case -1: // A before key was removed
before[muxedKey].forEach(function(beforeVal) {
results.push({ place: "del", key: muxedKey, val: beforeVal });
});
break;
case 0: // A mix of added/removed keys
// compare old & new vals
var itemDelta = {};
before[muxedKey].forEach(function(beforeVal) {
itemDelta[beforeVal] = itemDelta[beforeVal] || 0;
itemDelta[beforeVal]--;
});
after[muxedKey].forEach(function(afterVal) {
itemDelta[afterVal] = itemDelta[afterVal] || 0;
itemDelta[afterVal]++;
});
Object.keys(itemDelta).forEach(function(item) {
if (itemDelta[item] === 1) {
results.push({ place: "add", key: muxedKey, val: item });
} else if (itemDelta[item] === -1) {
results.push({ place: "del", key: muxedKey, val: item });
} else {
// itemDelta of 0 means it was unchanged between before/after
}
});
break;
default:
console.error("Calculated key delta of " + delta[muxedKey] +
" - this should never happen!");
break;
}
});
return results;
};
/**
* Shallow-compare two objects for equality: each key and value must be
* identical
*/
module.exports.shallowEqual = function(objA, objB) {
if (objA === objB) {
return true;
}
if (typeof objA !== 'object' || objA === null ||
typeof objB !== 'object' || objB === null) {
return false;
}
var keysA = Object.keys(objA);
var keysB = Object.keys(objB);
if (keysA.length !== keysB.length) {
return false;
}
for (var i = 0; i < keysA.length; i++) {
var key = keysA[i];
if (!objB.hasOwnProperty(key) || objA[key] !== objB[key]) {
return false;
}
}
return true;
};