JS 中的这个切片调用有什么问题？

Question

I write this line but get an error in response:

slice can't process there.

Why and how do I fix that?

function (row) {
    var r = Math.round(Object.values(row)[3] / Object.values(row)[4]);
    var t = Object.values(row)[2];
    var s = Math.round((t - r) / t * 100);
    return '<span id="up">${s.slice(0,2)}%</span>'
}

Answer 1

Your variable s is a number but the slice function requires a string . The solution would be to cast s into a string:

const slice = `${s}`.slice(0, 2);

Edit

To display a number with n decimals, you can multiply it by 10^n before rounding and then dividing it by the same number, cutting of anything after n decimals.

// display number with n decimals
const numberDisplay = (number, numberOfDecimals) => Math.round(number * Math.pow(10, numberOfDecimals)) / Math.pow(10, numberOfDecimals);

// your desired number display
const slice = numberDisplay(s, 2);