Add CSS with object

css.js

HTMLElement.prototype.css = function (style) {
  for (let k in style) {
    this.style[k] = style[k];
  }
};

// Example 1
document.body.css({
  backgroundColor: 'rgb(20,20,20)',
  fontFamily: 'Arial, sans-serif',
  fontSize: '16px'
});

// Example 2
var button = document.createElement('button');

button.css({
  color: '#fff',
  border: 0,
  padding: '10px 15px'
});

// Example 3
var div = document.querySelector('.wrap');

div.css({
  width: '1400px'
});

// Example 4
var container = document.getElementById('container');

button.addEventListener('click', e => {
  container.css({
    display: 'none'
  });
});