计算数组中相同元素的个数

Question

如下面的数组， 希望得到[{name: 'zhang', conut: 4},{name: 'wang', conut: 2},{name: 'liu', conut: 2}],或者[{zhang: 4},{wang: 2},{liu: 2}]谢谢了let arr= [             {name: 'zhang', age: '20'},             {name: 'wang', age: '22'},             {name: 'zhang', age: '20'},             {name: 'liu', age: '23'},             {name: 'liu', age: '23'},             {name: 'wang', age: '22'},             {name: 'zhang', age: '20'},             {name: 'zhang', age: '20'},         ]