JavaScript string contains

This is a simple function in JavaScript, I use it to check if a string contains another string.The different in this function is that the return value is the position+1.So you could use it in an If without to check the return value manually, just see my test from 1 to 3.

This is the function:

function string_contains(str,needle) {
return(str.indexOf(needle)+1);
}

Now we make a little test to see if it work:

//Test 1
if(string_contains("abcdef","a")){
console.log("abcdef contains a");
}else{
console.log("abcdef not contains a");
}
//Test 2
if(string_contains("abcdef","b")){
console.log("abcdef contains b");
}else{
console.log("abcdef not contains b");
}
//Test 3
if(string_contains("abcdef","z")){
console.log("abcdef contains z");
}else{
console.log("abcdef not contains z");
}

Seems good:

abcdef contains a
abcdef contains b
abcdef not contains z