问题
var developers = [
{ name: "Joe", age: 23 ,overallLevel: "high"},
{ name: "Sue", age: 28 ,overallLevel: "advanced" },
{ name: "Jon", age: 32 ,overallLevel: "high" },
{ name: "Bob", age: 24 ,overallLevel: "high" },
{ name: "Bob", age: 20 ,overallLevel: "advanced" }
]
Need count of overallLevel in the mentioned array using array.reduce() [high:3, advanced:2]
回答1:
You could just count them with an object.
var developers = [{ name: "Joe", age: 23, overallLevel: "high" }, { name: "Sue", age: 28, overallLevel: "advanced" }, { name: "Jon", age: 32, overallLevel: "high" }, { name: "Bob", age: 24, overallLevel: "high" }, { name: "Bob", age: 20, overallLevel: "advanced" }],
overallLevel = developers.reduce(function (r, a) {
r[a.overallLevel] = (r[a.overallLevel] || 0) + 1;
return r;
}, {});
console.log(overallLevel);
回答2:
Try this (you need no array.reduce()
to do that):
var
i,
count = {high: 0, advanced: 0},
developers = [
{ name: "Joe", age: 23 ,overallLevel: "high"},
{ name: "Sue", age: 28 ,overallLevel: "advanced" },
{ name: "Jon", age: 32 ,overallLevel: "high" },
{ name: "Bob", age: 24 ,overallLevel: "high" },
{ name: "Bob", age: 20 ,overallLevel: "advanced" }
];
for (i in developers) {
count[developers[i].overallLevel]++;
}
alert(JSON.stringify(count)); // Object { high=3, advanced=2}
来源:https://stackoverflow.com/questions/37565828/javascript-code-to-get-count-of-occurrence-of-objects-in-array-of-objects-using