JS For In Loop - thelastmile/FreeCodeCamp GitHub Wiki
The for..in statement iterates over the enumerable properties of an object, in 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. |
// Initialize object.
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