9.3.10 replaceAt函数

var k = String.format("%10.2f%%", d);            // k = " 1.23%"

var l = String.format("%3f %2f.", d);                // l = "1.234567 ."

var m = String.format("%.0d", 0);                     // m = ""

var n = String.format("%7d", "Int");                 // n = invalid

var o = String.format("%s", true);                     // o = "true"