Keep to one decimal place without rounding

Retain one significant digit without rounding;

For example: 199.999

is processed as follows

var str = parseFloat(199.999).toFixed(10);//Write 10 here to ensure that several decimal places are retained, after it The decimal point is 0 without rounding, so the result is what you want

var num = str.substring(0,str.lastIndexOf('.')+2)+"10,000";

After the following processing, num becomes 199.9