对象的计算属性

var Dep = { target: null};function defineComputed(obj, key, computeFunc) { computeFunc = computeFunc.bind(obj); Dep.target = computeFunc; var value = computeFunc(); Object.defineProperty(obj, key, { get: function() { return value; }, set: function() { // don’t do anything. can’t set computed funcs } })}function defineReactive(obj, key, val) { // all computed properties that depend on this var deps = []; Object.defineProperty(obj, key, { get: function() { // Check if there’s a computed property which ‘invoked’ // this getter. Also check that it’s already not a dependency if (Dep.target) { // add the dependency deps.push(Dep.target); Dep.target = null; } return val; }, set: function(newValue) { if (val === newValue) return; val = newValue; // notify all dependent computed properties deps.forEach(func => func()); } })}var obj = {};defineReactive(obj, ‘a’, 0);defineReactive(obj, ‘c’, 10);defineComputed(obj, ‘b’, function() { console.log(1); return this.a + this.c;});obj.a += 1;console.log(obj.b);obj.a += 1;console.log(obj.b);obj.a += 1;console.log(obj.b);参考文档：https://www.cnblogs.com/kidne…https://skyronic.com/blog/vue…