window is not defined

1.在vscode中运行以下代码显示错误：window is not defined。一直没想明白到底哪里有错，最后发现是自己的运行环境是node.js.window是web浏览器中才有的对象。所以在浏览器中运行以下代码就能正确显示。还包括以下情况

window.color = 'red';
let o = {
    color : 'blue'
}
let sayColor = function() {console.log(this.color);}

sayColor();
o.sayColor = sayColor;
o.sayColor();

　2.

let color = 'red';
let o = {
    color : 'blue'
}
let sayColor = function() {console.log(this.color);}

sayColor();//undefined
o.sayColor = sayColor;
o.sayColor();//blue