检查对象数组key是否为空并拼接

Question

I have an array of objects, in that there is an empty key with Boolean value, if the Boolean value is false then the array of objects should be spliced.

The below is the array structure:

 this.dataTobeDeleted= [{ NotificationID: "2180", Quantity: 1, NotificationName: "453", AlertNumber: "02/19/2020", "": true }, { NotificationID: "2182", Quantity: 1, NotificationName: "453", AlertNumber: "02/19/2020", "": false }, { NotificationID: "2181", Quantity: 1, NotificationName: "453", AlertNumber: "02/19/2020", "": false } ]

In the above array there is an empty string "key" if the key value is false then need to splice the array of objects using index.

Below is the code which I have tried:

 for (var i = 0; i < this.dataTobeDeleted.length; i++) { for (var val in this.dataTobeDeleted[i]) { if (val === "") { this.dataTobeDeleted[i]['isCheckedValue'] = this.dataTobeDeleted[i][""]; // insetring new key for empty key string delete this.dataTobeDeleted[i][""]; // Delete old key if (this.dataTobeDeleted[i].isCheckedValue === false) { this.dataTobeDeleted.splice(i, 1) } } } }

The above code is correct, but I need it in shorter way as the code I tried is in lengthier and when there is too much data it will create a problem.

I tried using filter also, but I am not getting the empty key to check the boolean value.

Answer 1

Use an array filter to remove the items you don't want:

this.dataTobeDeleted.filter(x => !!x[''])

DEMO: https://stackblitz.com/edit/router-template-1t2xz7

This will create a new array, keeping only those where the property '' is truthy. If you wanted to be stricter, you could use a strict boolean check:

this.dataTobeDeleted.filter(x => x[''] === true)

Answer 2

If your wanting to do this by mutating the original array using splice.

Make sure you loop the array backwards, this prevents issues of the loop index going out of sync as you mutate the array.

Example below..

 const dataTobeDeleted= [{ NotificationID: "2180", Quantity: 1, NotificationName: "453", AlertNumber: "02/19/2020", "": true }, { NotificationID: "2182", Quantity: 1, NotificationName: "453", AlertNumber: "02/19/2020", "": false }, { NotificationID: "2181", Quantity: 1, NotificationName: "453", AlertNumber: "02/19/2020", "": false } ]; for (let ix = dataTobeDeleted.length -1; ix >= 0; ix --) { if (!dataTobeDeleted[ix]['']) dataTobeDeleted.splice(ix, 1); } console.log(dataTobeDeleted);

Answer 3

它对我有用，请尝试一下

var newArr = dataTobeDeleted.filter((val) =>{return val[""] === true});

Answer 4

Quoting from MDN on Object.keys() :

The Object.keys() method returns an array of a given object's own enumerable property names, iterated in the same order that a normal loop would.

Then you can find the empty key and remove it with the delete method.

const deletedData = dataTobeDeleted.map((item, index) => {
    Object.keys(item).map(key => {
        if (!item['']) {
            dataTobeDeleted.splice(index, 1);
        }
    });
});

Answer 5

const isCheckedValue = obj => !!(obj[''])
this.dataToBeDeleted = dataToBeDeleted.filter(isCheckedValue)
console.log(result)

If you want to fix such objects simply use map

this.dataToBeDeleted = dataToBeDeleted.map(obj => {
   obj.isCheckedValue = obj['']
   delete obj[''] // mutations, not good :(
})

Answer 6

This is experimental, but you could also dabble with native ES6 iterator (using a generator) instead of looping through the data backwards.

 class ClassicIterator { constructor(list) { this.list = list; this.index = 0; } *[Symbol.iterator]() { while (this.index < this.list.length) { yield this.list[this.index]; this.index++; // Move forward } } remove() { this.list.splice(this.index, 1); this.index--; // Rollback } } class InPlaceFilter { constructor(opts) { this.list = opts.list; this.filterFn = opts.filterFn; } execute() { let it = new ClassicIterator(this.list); for (let item of it) { if (!this.filterFn(item)) { it.remove(); } } return this; } get() { return this.list; } } const data = [ { NotificationID:"2180", Quantity:1, NotificationName:"453", AlertNumber:"02/19/2020", "":true }, { NotificationID:"2181", Quantity:1, NotificationName:"453", AlertNumber:"02/19/2020", "":false }, { NotificationID:"2182", Quantity:1, NotificationName:"453", AlertNumber:"02/19/2020", "":false }, { NotificationID:"2183", Quantity:1, NotificationName:"453", AlertNumber:"02/19/2020", "":true } ]; let sameRef = new InPlaceFilter({ list : data, filterFn : (e) => e[''] === false }).execute().get(); console.log('Are the same?:', sameRef === data); // Same list!

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Simplified version:

 const InPlaceFilter = (opts) => { for (let i = opts.list.length - 1; i >= 0; i--) { if (!opts.filterFn(opts.list[i])) { opts.list.splice(i, 1); } } return opts.list; } const data = [ { NotificationID:"2180", Quantity:1, NotificationName:"453", AlertNumber:"02/19/2020", "":true }, { NotificationID:"2181", Quantity:1, NotificationName:"453", AlertNumber:"02/19/2020", "":false }, { NotificationID:"2182", Quantity:1, NotificationName:"453", AlertNumber:"02/19/2020", "":false }, { NotificationID:"2183", Quantity:1, NotificationName:"453", AlertNumber:"02/19/2020", "":true } ]; let otherRef = data.filter(e => e[''] === false); let sameRef = InPlaceFilter({ list : data, filterFn : (e) => e[''] === false }); console.log('Are the same?:', sameRef === data); // Same list! console.log('Are the same?:', sameRef === otherRef); // Not the same list!

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