<!DOCTYPE html><html><body><p id="demo">Click the button to locate where in the stringa specifed value occurs.</p><button onclick="myFunction()">Try it</button><script>function myFunction(){var str="Hello world, welcome to the universe.";var n=str.indexOf("welcome");document.getElementById("demo").innerHTML=n;}</script></body></html>希望本文所述对大家的javascript程序设计有所帮助。