Can any one help tell me what's wrong with my Javascript code?

var a = ["zero", "one", "two", "three"];
for (var i in a) {
  var sliced = a.slice(i + 1);
  console.log(sliced);
}

Can any one help tell me what's wrong with my Javascript code?

var a = ["zero", "one", "two", "three"];
for (var i in a) {
  var sliced = a.slice(i + 1);
  console.log(sliced);
}

the console log gives: ["one", "two", "three"],[],[],[]

but what I expected is: ["one", "two", "three"],["two", "three"],["three"],[]

So, why my code not work? And how should I code? Thanks a lot.

• javascript

• Why do you use for..in loop? – guest271314 Commented Jan 24, 2017 at 6:04
• Tip: log i + 1 to confirm it’s really 1, 2, 3, etc. – Sebastian Simon Commented Jan 24, 2017 at 6:05
• 2 @Rajesh The iteration variable in for..in is always a string. – Sebastian Simon Commented Jan 24, 2017 at 6:07
• @Rajesh Not sure why OP uses for..in, where current element of iterable property is a string, not a number? – guest271314 Commented Jan 24, 2017 at 6:10
• @guest271314 I guess OP is playing with different tools to learn. I have added a caveat in your answer. If not required, please revert the edit – Rajesh Commented Jan 24, 2017 at 6:14

4 Answers 4

You need to parse the string to number since for...in statement fetches object property which would be string. So in the second iteration, it would try to do a.slice('11')(string cocatenation '1' + 1 ==> '11') which returns an empty array.

var a = ["zero", "one", "two", "three"];
for (var i in a) {
  var sliced = a.slice(Number(i) + 1);
  console.log(sliced);
}

Since it's an array it's better to use a for loop with a counter variable i which starts from 1.

var a = ["zero", "one", "two", "three"];
for (var i = 1; i < a.length; i++) {
  var sliced = a.slice(i);
  console.log(sliced);
}

Use for loop to iterate arrays

var a = ["zero", "one", "two", "three"];
for (var i = 0; i < a.length; i++) {
  var sliced = a.slice(i + 1);
  console.log(sliced);
}

This will solve the problem :

why were you trying to do i+1?

var a = ["zero", "one", "two", "three"];
for (var i in a) {
  var sliced = a.slice(i);
  console.log(sliced);
}

var a = ["zero", "one", "two", "three"];
var i = 0;
while (i = a.length) {
   console.log(a);
   a.shift();
 }