Question

当我在下面的示例中使用数字时，我得到正确的返回/输出。

var array = [1,2,4,5,];
divBy2 = v => v / 2;
var result = array.map(divBy2);

当我在下面尝试这个时，我会得到NaV。

var array = [output];
divBy2 = v => v / 2;
var result = array.map(divBy2);

我的代码编写如下。基本上，我正在加载一个包含以下行的文本文件：

Numbers (999.000,999.000),(999.000,999.000),

然后我想创建一个数组并取这些数字并除以2.只返回没有整个字符串的数字。

var reader = new FileReader();

function readText(that){

        if(that.files && that.files[0]){
            var reader = new FileReader();
            reader.onload = function (e) {  
                var output=e.target.result;


output=output.split("\n").filter(/./.test,/Numbers/).join("\n").replace(/[^0-9.,]/g,'');

var array = [output];
divBy2 = v => v / 2;
var result = array.map(divBy2);

document.getElementById('inputTextToSave').innerHTML= output;

Answer 1

您不能在数组中放置字符串以使逗号分隔的语法工作，而是创建一个包含单个字符串（"1,2,3"）的数组。

＆＃13;

let output = "1,2,3";
var array = [output];//doesnt  work
//this creates  ["1,2,3"]
//array[0] === "1,2,3"
console.log("array", array);

var array2 = output.split(",");//works but creates string array
//this creates  ["1","2","3"]
//array2[0] === "1"
//array2[1] === "2"
//array2[2] === "3"
console.log("array2", array2)

var array3 = output.split(",").map(Number);//works and converts to number
//this creates  [1,2,3]
//array2[0] === 1
//array2[1] === 2
//array2[2] === 3
console.log("array3", array3)

//The closest to your attemp is eval() which shouldnt be used in normal cases
var array4 = eval("[" + output + "]");
console.log(array4)

＆＃13;

output是代码中的逗号分隔字符串（999.000,999.000,999.000,999.000,999.000,999.000,999.000,999.000,999.000），使用String.prototype,split将其拆分为数组

＆＃13;

let output = `Numbers (999.000,999.000),(999.000,999.000),
Numbers (999.000,999.000),(999.000,999.000),
Numbers (999.000,999.000),(999.000,999.000),
Numbers (999.000,999.000),(999.000,999.000)`;

output=output.split("\n").filter(/./.test,/Numbers/).join("\n").replace(/[^0-9.,]/g,'');
console.log(output);
let array = output.split(",");
console.log(array);
let divBy2 = v => v / 2;
let result = array.map(divBy2);
   console.log(result);

＆＃13;

要查看您的代码：

＆＃13;

let output = "1, 2, 3";
var array = [output];
console.log(array);//["1,2,3"]
divBy2 = v => v / 2;
var result = array.map(divBy2);
console.log(result);//[NaN]  as "1,2,3"/2 =NaN (not a number)

＆＃13;

JavaScript数组不返回数字

1 个答案: