JSON.parse convert string to array error

Question

So I am trying to write this function that calculates the average based on values in a string by first converting it to an array with JSON.parse. I am getting an error on the JSON.parse and I am not sure why.

"Uncaught SyntaxError: Unexpected token N" line: var elmt = JSON.parse('[' + string + ']');

    function averageRisk() {
            var sum = 0;
            var string = +health_grab; 
            // this returns a string from my database like this: 8,5,3,5,2,6,8,9

            var elmt = JSON.parse('[' + string + ']');

            console.log("healthLevels: " + elmt);

            for (var i = 0; i < elmt.length; i++) {
                        sum += parseInt(elmt[i].value, 10); 
            }

            if (isNaN(sum)) {
                        return false;
            }

            avg = Math.round(sum / elmt.length);

            console.log("Sum: " + sum);
            console.log("Average: " + avg);
    }

Answer 1

You have a unary plus + operator on +health_grab. This attempts to convert it into a number. This doesn't work and it produces NaN.

JSON.parse() tries and fails to parse NaN resulting in the error when it reaches the first character N.

Uncaught SyntaxError: Unexpected token N

Remove the + and it should fix the error.

Answer 2

I think you have a typo on your third line. You have an extra "+". When I test this in Node.JS I get the same error as you. Remove the "+" and it should work.

If this isn't a typo, what were you attempting to achieve with the prefixed "+"?