window is not defined

1.在vscode中運行以下代碼顯示錯誤：window is not defined。一直沒想明白到底哪里有錯，最后發現是自己的運行環境是node.js.window是web瀏覽器中才有的對象。所以在瀏覽器中運行以下代碼就能正確顯示。還包括以下情況

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