iterating an object properties

Question

is there a way to iterate an object properties and methods. i need to write a utility function like so:

function iterate(obj)
{
    //print all obj properties     
    //print all obj methods
}

so running this function:

iterate(String);

will print:

property: lenght
function: charAt
function: concat...

any ideas?

sixthgear · Accepted Answer · 2009-07-31 21:06:59Z

13

Should be as simple as this:

function iterate(obj) {
    for (p in obj) {
        console.log(typeof(obj[p]), p);
    }
}

Note: The console.log function is assuming you are using firebug. At this point, the following:

obj = {
    p1: 1, 
    p2: "two",
    m1: function() {}
};

iterate(obj);

would return:

number p1
string p2
function m1

answered Jul 31, 2009 at 21:06

sixthgear

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2 Comments

Amir Over a year ago

it seems that running your example works. However when i used the String class it didn't return anything. iterate(String); I also tried: var s = "sss"; iterate(s);

devios1 Over a year ago

When you iterate a string, it will step through each character. Try passing String(s) instead, to wrap the string in an object.

Community · Accepted Answer · 2017-05-23 12:22:10Z

6

See my answer in this other question, but you can't read built-in properties like that.

edited May 23, 2017 at 12:22

CommunityBot

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answered Jul 31, 2009 at 21:06

Peter Bailey

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Comments

Matthew Crumley · Accepted Answer · 2012-06-05 13:10:31Z

This only works in modern browsers (Chrome, Firefox 4+, IE9+), but in ECMAScript 5, you can get all the properties of an object with Object.getOwnPropertyNames. It just takes a little extra code to get the inherited properties from the prototype.

// Put all the properties of an object (including inherited properties) into
// an object so they can be iterated over
function getProperties(obj, properties) {
    properties = properties || {};

    // Get the prototype's properties
    var prototype = Object.getPrototypeOf(obj);
    if (prototype !== null) {
        getProperties(prototype, properties);
    }

    // Get obj's own properties
    var names = Object.getOwnPropertyNames(obj);
    for (var i = 0; i < names.length; i++) {
        var name = names[i];
        properties[name] = obj[name];
    }

    return properties;
}

function iterate(obj) {
    obj = Object(obj);

    var properties = getProperties(obj);

    for (var name in properties) {
        if (typeof properties[name] !== "function") {
            console.log("property: " + name);
        }
    }
    for (var name in properties) {
        if (typeof properties[name] === "function") {
            console.log("function: " + name);
        }
    }
}

Michael · Accepted Answer · 2009-07-31 21:08:11Z

0

You can use the for loop to iterate an object's properties.

Here is a simple example

var o ={'test':'test', 'blah':'blah'};

for(var p in o)
    alert(p);

answered Jul 31, 2009 at 21:08

Michael

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1 Comment

Buffalo Over a year ago

What if the property is a key for an object?

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