javascriptfor-loopconcatenationindexoflastindexof

For loop inside a string to concatenate the characters in a variable (without RegExp)- Javascript

I am trying to loop through a string variable and save every char inside an other variable. My code looks like this:

    var str = "hello world";
    var res = "";

    for (var i = str.indexOf("hello"); i <= str.lastIndexOf("hello"); i++) {
        res = res.concat(str.charAt(i));    
    }

    console.log("The result is: " + res);

It looks really logical for me, but it prints only the 1st letter. I expected it to say hello. What's the problem? Can't be done without a Regexp?

Solution

  • You need the length and the start postion for checking the index.

    var str = "bla bla hello world",
    res = "",
    i,
    l = "hello".length,
    p = str.indexOf("hello");

for (i = p; i < p + l; i++) {
    res += str[i];
}

console.log("The result is: " + res);