这里介绍JS常用的Math函数
-
PI
var pi = Math.PI;
console.log(pi);
// PI: 3.1415926
随机函数random
var value = Math.random();
console.log(value);
// 产生一个随机的[0, 1)小数
向下取整数floor
var value = Math.floor(98.76);
console.log(value);
//98 向下取整数
随机产生 一个[a, b]之前的整数
// [0, max-min)--> min + [min, max + 1)
function random_int (min, max) {
var value = min + (max - min + 1) * Math.random();
value = Math.floor(value);
return value;
}
var value = random_int(30, 50)
console.log(value);
三角函数, sin, cos, tan
参数是弧度
var value = Math.sin(Math.PI / 4);
console.log(value);
value = Math.cos(Math.PI / 4);
console.log(value);
value = Math.tan(Math.PI / 4);
console.log(value);
角度和弧度转换函数
//弧度radian --> 角度degree
function rad2deg(r) {
var degree = r * 180 / Math.PI;
return degree;
}
//角度degree --> 弧度radian
function deg2rad(degree) {
var r = (degree / 180) * Math.PI;
return r;
}
var value = rad2deg(Math.PI / 4);
console.log(value);
var value = deg2rad(90);
console.log(value);
反三角函数
value = Math.sin(deg2rad(90));
value = Math.asin(value);
console.log(rad2deg(value));
value = Math.cos(deg2rad(90));
value = Math.acos(value);
console.log(rad2deg(value));
value = Math.tan(deg2rad(88));
value = Math.atan(value);
console.log(rad2deg(value));
var r = Math.atan2(1, 1);
value = rad2deg(r);
console.log(value);
r = Math.atan2(-1, -1);
value = rad2deg(r);
console.log(value);
开根号
var value = Math.sqrt(3); // 根号2; 1.414
console.log(value);