Change properties of every item in an array?

问题

I need to set the value of every item in this array, counting up.

So, for example, path[0].value = 1, path[1].value = 2 etc...

EDIT: I'm looking for the most efficient way to do this.

I think a for loop is the best way, but I want to learn other ways. Can it be done with the map() method or forEach()? What about a for... in statement? I'd like to do it with pure JS, but if you can teach me a better way with jQuery, I'd be interested to learn that too.

Thanks in advance.

function Cell(x,y){
    this.xCoordinate = x;
    this.yCoordinate = y;
    this.value;
}
var path = [new Cell(0,0), new Cell(0,1), new Cell(0,2)];

回答1:

You can use a for loop or forEach:

for(var i=0; i<path.length; ++i)
  path[i].value = i+1;

path.forEach(function(cell, i) {
  cell.value = i + 1;
});

Better avoid for...in because of Why is using “for…in” with array iteration such a bad idea?.

回答2:

A simple for loop should work:

var path = [],
    len = 10;

for (
  var idx = 0;
  idx < len;
  path.push(new Cell(0,++idx))
)

回答3:

If you have an existing array, you can use map.

var path = [0,1,2].map( x => new Cell(0, x))

or to mutate

path = path.map( x => {
  x.value = x.yCoordinate - 1
  return x 
})

回答4:

<html>
<body>
<p id="demo"></p>
<script>
function Cell(x,y){
    this.xCoordinate = x;
    this.yCoordinate = y;
    this.value;
}
function setValues(element, index, array){
array[index].value = index+1;
}
var path = [new Cell(0,0), new Cell(0,1), new Cell(0,2)];
path.forEach(setValues);
document.getElementById("demo").innerHTML = path[2].value;
</script>
</body>
</html>

来源：https://stackoverflow.com/questions/35879307/change-properties-of-every-item-in-an-array

标签

javascript

jquery

arrays

foreach

for-in-loop