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<html lang="en"><head><meta charset="UTF-8"><title>Document</title></head><body><button οnclick="Function()">click</button><p id="demo">Paul,Paula,Pauline,paul,Paul</p><script>function Function(){ var str="Paul,Paula,Pauline,paul,Paul";var txt=str.replace(/\bPaul\b/g,"Ringo"); document.getElementById("demo").innerHTML=txt; }</script></body></html>