vuejs click outside element directive

click-outside.directive.js

export default {
    bind() {
        let click = this.click = e => {
            let target = e.target;
            let opacity = parseInt((window.getComputedStyle(this.el, null) || {}).opacity, 10) || 0;
            let hidden = this.el.style.display === 'none';
            if (opacity === 0 || hidden) {
                return;
            }
            let boundFn = this.vm[this.expression];
            let el = target;
            let found = el === this.el ? 1 : 0;
            let parent;
            while (!found) {
                parent = el.parentElement;
                if (parent === null) { // detached
                    return;
                }
                if (parent === this.el) {
                    found = 1;
                } else if (parent === document.body) { // guard
                    found = 2;
                }
                el = parent;
            }
            // not inside and callback is a function
            if (found !== 1 && typeof boundFn === 'function') {
                let id = target.id || '';
                boundFn(id, e);
            }
        };
        document.body.addEventListener('click', click, false);
    },
    unbind() {
        document.body.removeEventListener('click', this.click);
    }
};