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installproperty.js
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installproperty.js
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/*
* $Id: installproperty.js,v 0.8 2013/03/21 05:32:50 dankogai Exp dankogai $
*
* (c) 2013 Dan Kogai
*
* Licensed under the MIT license.
* http://www.opensource.org/licenses/mit-license
*
*/
(function(root) {
'use strict';
if (typeof Object.installProperty === 'function') return;
var create = Object.create;
if (!create || 'hasOwnProperty' in create(null)) {
throw new Error('ES5 unsupported');
}
var nameOfSafe = '__previousProperties__';
var hasOwnProperty = ''.hasOwnProperty;
var has = function(o, k) { return hasOwnProperty.call(o, k) };
var defineProperty = Object.defineProperty,
defineProperties = Object.defineProperties,
getOwnPropertyDescriptor = Object.getOwnPropertyDescriptor,
getOwnPropertyNames = Object.getOwnPropertyNames,
isArray = Array.isArray;
var isPrimitive = function(o) {
return Object(o) !== o;
};
// let the show begin!
function installProperty(target, prop, desc) {
if (prop === nameOfSafe) return;
if (isPrimitive(target)) {
throw new TypeError(target + ' is not an object');
}
if (!has(target, nameOfSafe)) { // create safe
try {
defineProperty(target, nameOfSafe, {
value: create(null),
// too fragile ?
writable: true,
configurable: true
});
} catch (e) {
throw e;
}
}
var safe = target[nameOfSafe], prev;
if (isArray(target)) { // array needs special andling :-(
// strictly check if prop is a stringified positive integer
if (prop.match(/^[0-9]+$/)) {
// and length will be updated
if (target.length <= prop * 1) {
// then save original length
prev = getOwnPropertyDescriptor(target, 'length');
if (!safe['length']) safe['length'] = [];
safe['length'].push(prev);
target.length = prop;
}
}
}
prev = getOwnPropertyDescriptor(target, prop);
if (prev) {
if (!prev.configurable) return false;
if (!prev.writable) return false;
}
desc.configurable = true;
desc.writable = true;
if (!safe[prop]) safe[prop] = [];
safe[prop].push(prev);
defineProperty(target, prop, desc);
return true;
};
function defaultProperty(target, prop, desc) {
return has(target, prop)
? false : installProperty(target, prop, desc);
};
function revertProperty(target, prop) {
if (prop === nameOfSafe) return;
var safe = target[nameOfSafe];
if (!safe) return;
if (!safe[prop]) return;
if (!safe[prop].length) {
delete safe[prop];
return;
}
var prev = safe[prop].pop();
if (!prev) {
delete target[prop];
} else {
var curr = getOwnPropertyDescriptor(target, prop);
defineProperty(target, prop, prev);
return curr;
}
};
function installProperties(target, descs) {
getOwnPropertyNames(descs)
.filter(function(k) {return k !== nameOfSafe})
.forEach(function(name) {
installProperty(target, name, descs[name]);
});
return target;
};
function defaultProperties(target, descs) {
getOwnPropertyNames(descs)
.filter(function(k) {return k !== nameOfSafe})
.forEach(function(name) {
defaultProperty(target, name, descs[name]);
});
return target;
};
function revertProperties(target, descs) {
descs = descs || target[nameOfSafe];
var prevs = create(null);
getOwnPropertyNames(descs)
.filter(function(k) {return k !== nameOfSafe})
.forEach(function(name) {
var prev = revertProperty(target, name, descs[name]);
if (prev) defineProperty(prevs, name, prev);
});
return prevs;
};
function restoreProperties(target) {
getOwnPropertyNames(target[nameOfSafe])
.filter(function(k) {return k !== nameOfSafe})
.forEach(function(name) {
var safe = target[nameOfSafe][name],
desc;
if (safe && safe.length){
desc = safe[0];
if (desc) {
// Firefox:
// defining the length property on an array
// is not currently supported
if (isArray(target) && name === 'length') {
target.length = safe[0].value;
} else {
defineProperty(target, name, safe[0]);
}
return;
}
}
delete target[name]
});
delete target[nameOfSafe];
};
var v2s = function(v) {
return {
value: v,
configurable: true,
writable: true
};
};
defaultProperties(Object, {
installProperty: v2s(installProperty),
defaultProperty: v2s(defaultProperty),
revertProperty: v2s(revertProperty),
installProperties: v2s(installProperties),
defaultProperties: v2s(defaultProperties),
revertProperties: v2s(revertProperties),
restoreProperties: v2s(restoreProperties)
});
})(this);