.split()

var str ="How are you doing today?";
document.write(str.split(" ") + "<br />")
document.write(str.split("") + "<br />")
document.write(str.split(" ",3))

輸出

How,are,you,doing,today?
H,o,w, ,a,r,e, ,y,o,u, ,d,o,i,n,g, ,t,o,d,a,y,?
How,are,you