<!DOCTYPE html>
<html lang="zh-cn">
<head>
<meta charset="UTF-8">
</head>
<body>
<script>
//fn(param) pass parameters, how to output "ab"
function fn(param){
if(param){
console.info("a");
}else{
console.info("b");
}
}
//This is correct, but output "ab" in console branch
//fn(fn(true));
//If you want to output "ab" in one line, you can refer to this method
fn(!function(){
console.info("ab");
console.info=function(){return;}
}());
</script>
</body>
</html>
Effect picture: