Error when redeclaring class in Firefox console but not in Chrome console

Question

class Picture {
    constructor(icon) {
        this.icon = icon

    }
}

When I run this code twice in the Chrome console it doesn't throw any errors. But when I try running it twice in the Firefox console it says Uncaught SyntaxError: redeclaration of let Picture. Why do the browsers behave differently?

score 1 · Accepted Answer · answered Feb 08 '22 at 15:52

A class can't be redefined. It is actually a block scoped variable.

If you're experimenting with code in a web browser, such as the Firefox Web Console (Tools > Web Developer > Web Console) and you 'Run' a definition of a class with the same name twice, you'll get a SyntaxError: redeclaration of let ClassName;

MDN docs

Redeclaration of let/const is allowed in chrome console. Run the below statement twice:

let x = 2;

Check this SO answer and this link from Chrome blog

Redeclaration within the same console line is not allowed though.

Error when redeclaring class in Firefox console but not in Chrome console

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