55 lines
1.3 KiB
Markdown
55 lines
1.3 KiB
Markdown
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---
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title: Check if an Object has a Property
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localeTitle: 检查对象是否具有属性
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---
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## 检查对象是否具有属性
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方法：
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* 完成此挑战的最简单方法是创建一个“ `ìf-statement`来检查对象是否包含所有用户，然后返回true或false语句。第一个解决方案就是这样做的。
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* 第二个解决方案以完全相同的方式工作，只有它在函数内使用1行代码 - `Conditional(ternary)-Operator` - `Conditional(ternary)-Operator` 。
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[developer.mozilla.org](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Conditional_Operator)对三元运算符进行了更深入的分析。
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### 方案1：
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```javascript
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let users = {
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Alan: {
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age: 27,
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online: true
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},
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Jeff: {
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age: 32,
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online: true
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},
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Sarah: {
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age: 48,
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online: true
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},
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Ryan: {
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age: 19,
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online: true
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}
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};
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function isEveryoneHere(obj) {
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// change code below this line
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if(users.hasOwnProperty('Alan','Jeff','Sarah','Ryan')) {
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return true;
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}
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return false;
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// change code above this line
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}
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console.log(isEveryoneHere(users));
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```
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### 方案2：
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```javascript
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function isEveryoneHere(obj) {
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return (users.hasOwnProperty('Alan','Jeff','Sarah','Ryan')) ? true : false;
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}
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```
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