循环检查是否在最后一次迭代？

Question

How do I check if I'm on the last iteration of this loop? I'm sorry for asking this question. I'm used to programming in VB.NET and javascript seems very cryptic by nature.

if (QuerySplit.length > 1) {
   var NewQuery
   for (i=0; i<QuerySplit.length; i++)
   {
       // if we're not on the last iteration then
       if (i != QuerySplit.length) {
           // build the new query
           NewQuery = QuerySplit[i].value + " AND "
       }
    }
}

Answer 1

Your i is always smaller than QuerySplit.length - that's your loop condition. In the last iteration it will have a value of QuerySplit.length-1 , that's what you can check against:

if (i < QuerySplit.length - 1)

Btw, you'd do better to use the join Array method for what you're trying to do:

var NewQuery = QuerySplit.map(function(x){return x.value;}).join(" AND ");

Answer 2

Take note that you need var NewQuery = ""; and check for length - 1. Also, the last if statement is just a guess of what you probably want to do:

if (QuerySplit.length > 1) {
  var NewQuery = "";
  for (i = 0; i < QuerySplit.length; i++) {
    // if we're not on the last iteration then
    if (i != QuerySplit.length - 1) {
      // build the new query
      NewQuery += QuerySplit[i].value + " AND "
    } else {
      NewQuery += QuerySplit[i].value;
    }
  }
}

If QuerySplit.length is 4, then:

0, 1, 2, 3

...are the indexes. So you want to check for when the index is 3 and that's your last iteration.

Answer 3

The array is 0-based. This means if there are 3 items in the array, your indexes will be 0,1,2 . The last one is one less than the length.

You'll have to check like this: (i < QuerySplit.length -1)