javascript - 如何计算 Angular 或javascript中分组数组的长度？

Question

array = [  
  {
    name: 'hello 1',
    checked: true,
    color:'#1ac3ec',
    group:'first category'
  },
  {
    name: 'hello 2',
    checked: true,
    color:'#7dc55c',
    group:'first category'
  },
  {
    name: 'hello 3',
    checked: true,
    color:'#005073',
    group:'second category'
  },{
    name: 'hello 4',
    checked: true,
    color:'#fbb330',
    group:'second category'
    }
]

我想得到每组的长度。我们怎样才能得到它？

例如 array.group['second category'].length

Answer 1

你可以使用 array.filter:

var array = [  
  {
    name: 'hello 1',
    checked: true,
    color:'#1ac3ec',
    group:'first category'
  },
  {
    name: 'hello 2',
    checked: true,
    color:'#7dc55c',
    group:'first category'
  },
  {
    name: 'hello 3',
    checked: true,
    color:'#005073',
    group:'second category'
  },{
    name: 'hello 4',
    checked: true,
    color:'#fbb330',
    group:'second category'
    }
];

var len1 = array.filter(e => e.group === 'first category').length;
console.log(len1);
var len2 = array.filter(e => e.group === 'second category').length;
console.log(len2);