英文:
Find the number of undefined properties in an object with Lodash
问题
我需要找出未定义的属性数量，在这种情况下是2。
英文:
let x = {
"name": undefined,
"value": "tr",
"prop1": undefined,
"prop2": "test",
"prop3": 123
};
I need to find the number of properties that are undefined, so in this case 2.
答案1
得分: 0
使用常规的JS：
好的评论指出，我们确实可以立即进行过滤；更高效的方法是：
Object.values(x).filter(v => v === undefined).length
使用Lodash
_.filter(x, (v, k) => v === undefined).length
英文:
With regular JS:
Good comments pointed out that we can indeed immediately filter; more efficient:
Object.values(x).filter(v=> v === undefined).length
With Lodash
_.filter(x, (v, k) => v === undefined).length
答案2
得分: 0
你可以使用 _.countBy() 来获得一个包含值在原始对象 (data) 中出现次数的对象 (counts)。然后，你可以从 counts 对象中获取 undefined 值的数量：
const data = { "name": undefined, "value": "tr", "prop1": undefined, "prop2": "test", "prop3": 123 };
const counts = _.countBy(data);
console.log(counts);
console.log(counts.undefined);
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.21/lodash.min.js" integrity="sha512-WFN04846sdKMIP5LKNphMaWzU7YpMyCU245etK3g/2ARYbPK9Ub18eG+ljU96qKRCWh+quCY7yefSmlkQw1ANQ==" crossorigin="anonymous" referrerpolicy="no-referrer"></script>
英文:
You can use _.countBy() to get an object (counts) that contains the number of time a value appears in the the original object (data). You can then get the number of undefined values from the counts object:
<!-- begin snippet: js hide: false console: true babel: false -->
<!-- language: lang-js -->
const data = { "name": undefined, "value": "tr", "prop1": undefined, "prop2": "test", "prop3": 123 };
const counts = _.countBy(data);
console.log(counts);
console.log(counts.undefined);
<!-- language: lang-html -->
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.21/lodash.min.js" integrity="sha512-WFN04846sdKMIP5LKNphMaWzU7YpMyCU245etK3g/2ARYbPK9Ub18eG+ljU96qKRCWh+quCY7yefSmlkQw1ANQ==" crossorigin="anonymous" referrerpolicy="no-referrer"></script>
<!-- end snippet -->
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