带有数组的 Angular Javascript 对象，循环遍历并获取每个数组的长度？

Question

I'm trying to create a dataset from an API backend I've set up in my project. I've already managed to group my api call on the date but now I need to check the length of each date array that is created by lodash.

How would I do this because every attempt I've tried so far has failed. The image I've included shows the console.log after I have grouped my result, it also shows the amount of entries in each array which is exactly what I want to retrieve.

Current code, I removed my attempt at solving this problem because I would only get back undefined results.

        ngOnInit() {
        this._estimateService.getEstimates()
            .subscribe(estimateData => {
                const groupedEstimateData = groupBy(estimateData, 'estimate_date');
                console.log(groupedEstimateData);
            });
        }

Example of desired result:

2019-12-09, 47
2019-12-10, 6
etc

Image:

Answer 1

I'm not sure of what you mean by "checking the length". Here is an example of your desired console.log output

ngOnInit() {
        this._estimateService.getEstimates()
            .subscribe(estimateData => {
                const groupedEstimateData = groupBy(estimateData, 'estimate_date');
                Object.entries(groupedEstimatesData).map(([date, estimatedData]) => {
                    // do what you want there with each line
                    console.log(date, estimatedData.length);
                });
            });
        }

You can have a look at Object.entries and map methods.

Good luck

Answer 2

You could do something like:

const groupsWithCounts = Object.keys(groupedEstimateData).map(key => {
    [key]: groupedEstimateData[key],
    total: groupedEstimateData[key].length
})

Now groupsWithCounts will be an array of objects with this structure:

{
    2019-12-9: [item, item, item, ...], // the original items
    total: 47 // the total count of items
}

Answer 3

You can do this simply with :

 const dates = Object.keys(groupedEstimateData); let output = {}; dates.forEach( date => output[date] = groupedEstimateData[date].length );

Object.keys(groupedEstimateData) will give you an array ["2019-12-09", "2019-12-10", etc]

You then iterate this array to construct this output object :

{
    "2019-12-09" : 47,
    "2019-12-10" : 6,
    etc
}