It’s that modern ES6 syntax that I think is the shorthand that is being complained about by the website’s interpreter.
I recommend trying to resolve matters by putting the property keys in quotes:
let person = {
"name": name,
"material": material,
"assemble": assemble,
"duration": duration
};
And if issues continue, please let us know of the page where this is happening so that a deeper investigation can take place.