JSNI function in GWT to format numbers

public class NumberUtil {
 
 public static native String toFixed(double d, int fixed)/*-{
  return d.toFixed(fixed);
 }-*/;
 
 public static native String toPrecision(double d, int precision)/*-{
  return d.toPrecision(precision);
 }-*/;

}

see also this article.

Format numbers in javascript

var num = 1;
var result = num.toFixed(2); // result = 1.00

num = 123.4567;
result = num.toFixed(3); // result = 123.456

num = 123.4567;
result = num.toPrecision(4); // result = 123.4

num = 123.4567;
result = num.toPrecision(3); // result = 123

num = 555.55;
result = num.toPrecision(2); // result will equal 5.6e+2

see also this article.