ReactJS TypeError：无法读取未定义的属性

Question

I have this code right here, that works in this online text editor: https://codesandbox.io/s/o4n0v203vy

In the npm console , everything is okay:

But in the browser , this happens:

What logs in the console, when i do export var renderTree = (node, setActiveNode, activeNode) => { console.log(node && node.type, 'look here');

I can't figure out why is this happening. Any help is appreciated! Thanks!

Answer 1

The variable node is undefined so doesn't have a property called type .

Change your check to

if(node && node.type === 'file'){
    ...
}

Answer 2

您可能正在浏览器中运行源文件，而不是已构建的文件。