Why does having [].map with curly brackets change the way it works?

Question

So, basically I have this:

Array.prototype.toString = function() {
    return (\"[\" + this.map(thing => thing = \'\"\' + thing + \'\"\').join(\', \') + \"]\"         


        

Answer 1

You do not return something in the block statement of the arrow function

() => {
    // code
    return 42; // return is required in block statment
}


() => 42 // return is implicit

Array.prototype.toString = function() {
    return ("[" + this.map(thing => { return thing = '"' + thing + '"'}).join(', ') + "]")
};

console.log(['foo', 'bar'].toString())

Shorter, without assignment to thing

Array.prototype.toString = function() {
    return ("[" + this.map(thing => '"' + thing + '"').join(', ') + "]")
};

console.log(['foo', 'bar'].toString())