I'm trying to figure out how the setting of a property is being intercepted in jsdom's CSSStyleDeclaration implementation. This is being done for validation purposes. I want to know where this validation is happening. github link
This is the line where the setting is happening.
this[lowercaseName] = value;
I'm only aware of one method that can be used to intercept this action. Which is usage of Proxy Object. But the object in question is not a proxy object.
Hence Question: What are the other ways of intercepting(man in the middle) the action of setting properties on an object?
To confirm interception is happening:
const {CSSStyleDeclaration} = require('cssstyle')
const decl = new CSSStyleDeclaration()
decl.setProperty('background-color', 'invalid-value')
decl.getPropertyValue('background-color') // '' returns empty string
decl.setProperty('background-color', '#333')
decl.getPropertyValue('background-color') // '#333'
What are the other ways of intercepting(man in the middle) the action of setting properties on an object?
The set syntax binds an object property to a function to be called when there is an attempt to set that property.
In your particular example the colour validation is done by a parseColor function called by the background-color setter.