1.6 KiB
1.6 KiB
| title |
|---|
| For...In Loop |
The for...in statement iterates over the enumerable properties of an object, in an arbitrary order. For each distinct property, statements can be executed.
for (variable in object) {
...
}
| Required/Optional | Parameter | Description |
|---|---|---|
| Required | Variable | A different property name is assigned to variable on each iteration. |
| Optional | Object | Object whose enumerable properties are iterated. |
Examples
// Initialize object.
var a = { "a": "Athens", "b": "Belgrade", "c": "Cairo" };
// Iterate over the properties.
var s = "";
for (var key in a) {
s += key + ": " + a[key];
s += "<br />";
}
document.write (s);
// Output:
// a: Athens
// b: Belgrade
// c: Cairo
// Initialize the array.
var arr = new Array("zero", "one", "two");
// Add a few expando properties to the array.
arr["orange"] = "fruit";
arr["carrot"] = "vegetable";
// Iterate over the properties and elements.
var s = "";
for (var key in arr) {
s += key + ": " + arr[key];
s += "<br />";
}
document.write (s);
// Output:
// 0: zero
// 1: one
// 2: two
// orange: fruit
// carrot: vegetable
// Efficient way of getting an object's keys using an expression within the for-in loop's conditions
var myObj = {a: 1, b: 2, c:3}, myKeys = [], i=0;
for (myKeys[i++] in myObj);
document.write(myKeys);
//Output:
// a
// b
// c