How is sticky-position finding out native support?

[juhaelee]

const nativeSupport = (function(){      
        if (this.isSupported !== null) {
            return this.isSupported;
        } else {
            const style = document.createElement('test').style;
            style.cssText = ['-webkit-', '-ms-', ''].map(prefix => `position: ${prefix}sticky`).join(';');
            this.isSupported = style.position.indexOf('sticky') !== -1;
            return this.isSupported;
        }
    }).bind({isSupported: null});

Wouldn't isSupported always be null, so wouldn't the else clause always be executed?

@jackmoore

[jackmoore]

The first time the function is called, the else clause will execute and set this.isSupported to be either true or false. Know that bind is being invoked just once in the creation of the function, and each call to the function references the same object that was passed to bind, so value of this.isSupported is persistent between calls.