JavaScript 数组在索引处拆分

Question

I have an array like:

var arr = ['Number 1', 'name', 'Number 2', 'name']

How can I get a string from this array that looks like this:

var str = 'Number 1: name, Number 2: name'

Answer 1

For this, you'd probably want Array#reduce , see the comments:

 // The array var arr = ['Number 1', 'name', 'Number 2', 'name'] // Start with no delimiter var delim = ""; // Array#reduce calls the callback once for each entry, passing in // the accumulator as the first argument and the entry as the second var str = arr.reduce(function(acc, entry) { // Add this entry onto the accumulator acc += delim + entry; // Toggle between ", " and ": " as the delim (the first time we have // "", which means we'll switch to ": ") delim = delim === ", " ? ": " : ", "; // Return the new value of the delim return acc; }, ""); // ^^---- initial value of the accumulator is blank document.body.innerHTML = "<pre>" + str + "</pre>";

Alternately, you can do it with the other variant of reduce where you don't give an initial value for the accumulator:

 // The array var arr = ['Number 1', 'name', 'Number 2', 'name'] // Start with the first delimiter we want to use var delim = ": "; // Array#reduce calls the callback slightly differently the // first time: It passes entry 0 as the first argument and entry 1 // as the second. From then on it keeps passing the accumulator. var str = arr.reduce(function(acc, entry) { // Add this entry onto the accumulator acc += delim + entry; // Toggle between ", " and ": " as the delim (the first time we have // "", which means we'll switch to ": ") delim = delim === ": " ? ", " : ": "; // Return the new value of the delim return acc; }); document.body.innerHTML = "<pre>" + str + "</pre>";

Or actually, you could use map and join :

 // The array var arr = ['Number 1', 'name', 'Number 2', 'name'] // Append the desired delimiter to each entry except the last, // then join the resulting array var str = arr.map(function(entry, index) { if (index < arr.length - 1) { entry += index % 2 == 1 ? ", " : ": "; } return entry; }).join(""); document.body.innerHTML = "<pre>" + str + "</pre>";

Answer 2

You can do it by,

var arr = ['Number 1', 'name', 'Number 2', 'name'],res ="";
for(var i=0,len=arr.length;i<len;i+=2){
  res += arr[i] + ":" + arr[i+1] + ((i+2 != len) ? "," : "");
}

set your for loop's step as 2. During iteration get the array's values related to current index and current index + 1 . Concatenate it by giving a delimiter as : . And your job is done.

DEMO

Answer 3

You can use .join() with .replace() :

 var arr = ['Number 1', 'name', 'Number 2', 'name']; var s = arr.join(',').replace(/(\\d)+/g, '$1:').replace(/(:,)/g, ':'); document.write('<pre>'+s+'</pre>')

Answer 4

This code will give you correct output as needed ->

    var str = "";
    var arr = ['Number 1', 'name', 'Number 2', 'name'];
    var i=0;
    while(i<arr.length)
   {

   str += i==0 ? "" : ","
    str+=arr[i];
    i++;
    str+=":";
    str+=arr[i];

   }

Answer 5

You shouldn't use string concatenation when there is another solution, simply because it's less readable and harder to maintain.

 var arr = ['Number 1', 'name', 'Number 2', 'name']; var str = Array.from({length: arr.length / 2}).map(() => arr.splice(0, 2).join(' :')).join(', '); document.body.innerHTML = `<pre>${str}</pre>`;