js保留两位小数

此方法会改变数据类型变为string，但是不会四舍五入，用的是字符串截取，不够两位小数补零

    let value = 5.53
    let numStr = Number(value).toString()
    let index = numStr.indexOf('.')
    let transformVal = ""
    if (index == '-1') {
        transformVal = numStr + ".00"
    } else {
        let numbers = (numStr.slice(index + 1)).length
        switch (numbers) {
            case 1:
                transformVal = numStr + '0'
                break;
            case 2:
                transformVal = numStr
                break;
            default:
                transformVal = numStr.slice(0, index + 3)
                break;
        }
    }
    console.log(transformVal);