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/** | |
* | |
* Creating configurable property | |
* | |
* @param {Object} obj - Object to which should be assigned a new property | |
* | |
* @param {String} name - property name | |
* @param {object} descriptor - property settings | |
* @param {Function} descriptor.get - fn fires when receive prop value | |
* @param {Function} descriptor.set - fn fires when assign value to prop | |
* @param {Object} descriptor.default - Initial value for descriptor. | |
*/ | |
const descriptor = (obj, name, descriptor) => { | |
Object.defineProperties(obj, { | |
[`_${name}`]: { | |
enumerable: false, | |
configurable: true, | |
writable: false, | |
value: descriptor.default || true | |
}, | |
[name]: { | |
enumerable: true, | |
configurable: false, | |
get: () => { | |
descriptor.get && descriptor.get(obj[`_${name}`]); | |
return obj[`_${name}`]; | |
}, | |
set: (val) => { | |
if (descriptor.final) return; | |
setWritable(obj, `_${name}`, true); | |
obj[`_${name}`] = val; | |
setWritable(obj, `_${name}`, false); | |
descriptor.set && descriptor.set(val); | |
} | |
} | |
}); | |
obj[name] = descriptor.hasOwnProperty('default') ? descriptor.default : true; | |
}; | |
/** | |
* Change value of writable at descriptor if a prop configurable=true | |
* | |
* @param {Object} obj - Object in which should be changed prop 'writable' at descriptor | |
* @param {String} name - property name | |
* @param {Boolean} isWritable - value of writable prop | |
*/ | |
const setWritable = (obj, name, isWritable) => { | |
let descr = Object.getOwnPropertyDescriptor(obj, name); | |
if (descr.configurable) { | |
descr.writable = isWritable; | |
Object.defineProperty(obj, name, descr); | |
} | |
}; | |
let car = {}; | |
descriptor(car, 'weight', {final: true, default: 2000}); | |
descriptor(car, 'color', {final: true, default: 'coral'}); | |
descriptor(car, 'driver', {default: 'Jason Statham'}); | |
car.weight = 10; | |
car.color = 'white'; | |
car.driver = 'Andrey Bezhinaru'; | |
console.log(car.weight); // 2000 | |
console.log(car.color); // coral | |
console.log(car.driver); // Andrey Bezhinaru instead of 'Jason Statham' |
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