Introduction

A simple node.js module that recursively iterates over an object and makes the properties read-only. This is useful for values in objects that are never to change.

In the past, if you set a constant property, the assignment silently failed. Now, assignments to constant properties throw exceptions.

Installation

$ npm install const-obj

API

The following are exported from the const-obj module:

• makeObjConst()
• makePropConst()

makeObjConst(obj)

Recursively makes each property in the object and its sub-objects immutable. This function returns the object upon success and false upon failure.

makePropConst(obj, property)

Make a property immutable (assuring it cannot be changed from the current value). This operation cannot be un-done. This function returns the object on success and false on any failure.

Examples

var assert = require('assert');
var makeObjConst = require('const-obj').makeObjConst;
var obj = {
    a: 111,
    b: '222',
    c: { d: 333 } };
makeObjConst(obj);

try {
    obj.a = 222;            // this will throw
} catch (err) {
    assert.ok(err.message === 'Cannot assign to read only property \'a\' of #<Object>');
}
assert.ok(obj.a === 111);

The above code will throw because the values cannot be changed.

    var makePropConst = require('const-obj').makePropConst;
    var obj = { alpha: '0', beta: false };
    makePropConst(obj, 'alpha');

    try {
        obj.alpha = 678;
    } catch(err) {
        assert.ok(err.message === 'Cannot assign to read only property \'alpha\' of #<Object>');
    }
    assert.ok(obj.alpha === '0');

    obj.beta = true;
    assert.ok(obj.beta === true);

The above code will throw because the property is constant and cannot be changed.

License

The MIT License (MIT)

Copyright (c) 2013,2014 Edmond Meinfelder

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.