I have an javascript object of arrays like,
var coordinates = {
"a": [
[1, 2],
[8, 9],
[3, 5],
[6, 1]
],
"b": [
[5, 8],
[2, 4],
[6, 8],
[1, 9]
]
};
but coordinates.length returns undefined.
Fiddle is here.
That's because coordinates is Object not Array, use for..in
var coordinates = {
"a": [
[1, 2],
[8, 9],
[3, 5],
[6, 1]
],
"b": [
[5, 8],
[2, 4],
[6, 8],
[1, 9]
]
};
for (var i in coordinates) {
console.log(coordinates[i])
}
or Object.keys
var coordinates = {
"a": [
[1, 2],
[8, 9],
[3, 5],
[6, 1]
],
"b": [
[5, 8],
[2, 4],
[6, 8],
[1, 9]
]
};
var keys = Object.keys(coordinates);
for (var i = 0, len = keys.length; i < len; i++) {
console.log(coordinates[keys[i]]);
}
coordinates is an object. Objects in javascript do not, by default, have a length property. Some objects have a length property:
"a string - length is the number of characters".length
['an array', 'length is the number of elements'].length
(function(a, b) { "a function - length is the number of parameters" }).length
You are probably trying to find the number of keys in your object, which can be done via Object.keys():
var keyCount = Object.keys(coordinates).length;
Be careful, as a length property can be added to any object:
var confusingObject = { length: 100 };
(function(){}).length is number of arguments. Thanks for your sharing.http://jsfiddle.net/3wzb7jen/2/
alert(Object.keys(coordinates).length);
