Need Help With Execute JS in A Config

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i am trying to create a config for a game so that it auto buys a product after successful login, but i honestly dont know what i am doing. the return response from json when i do html request and then i put the java command to buy product.however i keep getting "is not defined" error. i did try defining it but i think i put it in the wrong place. im not sure i left a screenshot of what i came up with. hopefully someone can help.