JavaScript中数组内的平均值

Question

The JSON:

[{"id":"1","user":"001","answer":"1,1,3,2,2,1,3,2"},
{"id":"2","user":"002","answer":"2,3,3,2,1,1,3,2"},
{"id":"3","user":"003","answer":"3,5,3,5,3,1,3,2"}]

The JavaScript:

jQuery.ajax({
    url: "file.json",
    type: "POST",
    dataType: "json",
    async: false,
    success: function (data) {
    var arr = [];
    for (i = 0; i < data.length; i++) { 
        arr.push(data[i].answer);
    }
    console.log(arr);
});

What I'm trying to do is make an average of each value from the 3 answer s, which in case will give these 8 averages:

2,3,3,3,2,1,3,2

Answer 1

 const arrAvg = arr => arr.reduce((a,b) => a + b, 0) / arr.length; console.log(arrAvg([1,2,3,4,5])); 

Answer 2

You may use:

• Array.prototype.map()
• Array.prototype.reduce()
• String.prototype.split()
• Arrow functions

---

Working Example:

 let data = [{"id":"1","user":"001","answer":"1,1,3,2,2,1,3,2"}, {"id":"2","user":"002","answer":"2,3,3,2,1,1,3,2"}, {"id":"3","user":"003","answer":"3,5,3,5,3,1,3,2"}]; let result = data.map(o => { /* Split the string into array using , delimiter */ let a = o["answer"].split(","); /* * Return average of array by first creating sum using .reduce() and * then dividing by number of array elements. */ return a.reduce((a,c) => (Number(c) + a), 0) / a.length; }); console.log(result); 

Answer 3

create a new array from the answer then sum all the values and divide by its size

 var res = [{ "id": "1", "user": "001", "answer": "1,1,3,2,2,1,3,2" }, { "id": "2", "user": "002", "answer": "2,3,3,2,1,1,3,2" }, { "id": "3", "user": "003", "answer": "3,5,3,5,3,1,3,2" } ]; res.forEach(function(item) { //creating array from the string var imtArray = item.answer.split(','); //summing the element var avg = imtArray.reduce(function(p, q) { // converting string to number return +p + +q }) console.log(avg / imtArray.length) }) 

Answer 4

You're getting the answer , but now you need to split it by commas and parse it to a number. This gives you an array for each answer , now you can simply iterate through each one and add the numbers then divide them by their count (ie array length) to calculate the average.

Note: the values in the answers are strings, so make sure you convert them to numbers before you add them together, otherwise you will be adding them together as characters.

 var data = [{"id":"1","user":"001","answer":"1,1,3,2,2,1,3,2"}, {"id":"2","user":"002","answer":"2,3,3,2,1,1,3,2"}, {"id":"3","user":"003","answer":"3,5,3,5,3,1,3,2"}] var arr = []; for (var i = 0; i < data.length; i++) { var d = data[i].answer.split(","); var sum = 0; for (var j = 0; j < d.length; j++) { sum += parseInt(d[j]); } arr.push(sum / d.length); } console.log(arr); 

It seems from your comments that instead of the average of values in each of the three answer s, you actually want the average of each value from the three answer s. Similar to the code above, you just need to make a little change. You'll have to iterate and add the values of each answer first, then iterate again and calculate the averages:

 var data = [{"id":"1","user":"001","answer":"1,1,3,2,2,1,3,2"}, {"id":"2","user":"002","answer":"2,3,3,2,1,1,3,2"}, {"id":"3","user":"003","answer":"3,5,3,5,3,1,3,2"}] var arr = []; for (var i = 0; i < data.length; i++) { var d = data[i].answer.split(","); for (var j = 0; j < d.length; j++) { d[j] = parseInt(d[j]); } if (arr.length == 0) arr = d; else { for (var j = 0; j < d.length; j++) { arr[j] += d[j]; } } } for (var i = 0; i < arr.length; i++) { arr[i] = arr[i] / data.length; } console.log(arr); 

Note: This assumes that each answer has the exact same number of values.