Query Selector Utilities ES6-ES2015

export function querySelectArray(selector, el = document) {
    // Usage: fn(selector, document.body)
    // Returns [el1, el2, ...]
    return Array.prototype.slice.call(el.querySelectorAll(selector));
}

export function querySelectArrayByElementArray(selector, els, removeDuplicates=true){
    // Usage: fn(selector, [document.body, document.head])
    // Returns [elementFromBody1, elementFromBody2, elementFromHead1, ...]
    
    let arr = Array.prototype.concat.apply([], Array.prototype.slice.call(els).map( (el) => querySelectArray(selector, el) ));
    if(removeDuplicates) arr = arr.filter( (el, index, self) => index === self.indexOf(el) );
    return arr;
}