Write a function firstWord, taking a string and returning the first word in that string. The first word are all characters up to the first space

Question

function firstWord (go and run) {
 let text = "go and run";
 let firstBlank = text.substr(0, 2);
 return firstBlank;
 }

Why is this giving me wrong answer? Can any one explain the solution please? hint:-

function firstWord(s) {
  let firstBlank = s.indexOf(' ');
  return s.substr(0, firstBlank);
}

First of all, [`substr`](//developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/String/substr) is deprecated. Don’t use it. Next, consider what happens when the input is `"word"`. Read the docs: [`indexOf`](//developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/String/indexOf), [`substring`](//developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/String/substring), [`split`](//developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/String/split). Use the [browser console (dev tools)](//webmasters.stackexchange.com/q/8525) (hit `F12`). — Sebastian Simon, Jan 02 '22 at 12:02
@SebastianSimon is right - also explain what trouble you had with your first attempt? what was wrong with the result? — Always Learning, Jan 02 '22 at 12:03
Related: [How to grab substring before a specified character jQuery or JavaScript](/q/9133102/4642212). — Sebastian Simon, Jan 02 '22 at 12:04

score 1 · Accepted Answer · answered Jan 02 '22 at 12:17

There are several problems with your code:

go and run is not a valid parameter declaration in the function header. There is confusion here with the parameter and the string value that you expect the function to be called with. In the function header you should list the parameter(s) with variable names. Since the function should be called by passing a string, you could name that variable phrase, or text or something else that is descriptive.
let text = "go and run"; should not appear in the function. The function should work for any string, so it should not be hard-coded to "go and run". The parameter variable will have the actual string that the function is called with.
let firstBlank = text.substr(0, 2); is again focusing on one particular string. It actually doesn't search for a space at all. You -- as programmer -- tell it that the first word is 2 characters long. Your function then might as well just do return "go". But you should really support any string, and then let the code find out how long the first word is by scanning the string for the first space or end of the string.
substr (also in the second code block) is a deprecated function. Use slice instead.

The second code snippet does the job better, but it still goes wrong when the given string only contains one word. In that case, it will return the wrong answer.

Here is a correction to that second function, but using a more descriptive parameter variable:

function firstWord(text) {
  let firstBlank = text.indexOf(' ');
  if (firstBlank == -1) { // There is no space at all -- return the whole string
    return text;
  } 
  return text.slice(0, firstBlank);
}

NB: Using split a shorter solution code is possible.

Write a function firstWord, taking a string and returning the first word in that string. The first word are all characters up to the first space

1 Answers1