Values ​​as a condition

Muffin began working on another program: “Can I start the project?” And we will test it and fix the errors, if necessary.

The program checks several conditions and gives an expert opinion. First, it checks to see if any of the developers are on vacation. We need to test this condition with different types of data.

The fact of the matter is that we receive information on vacations from managers in completely different formats. Some will immediately say that the developers are still on vacation, that is, will give us true, and some will not understand the question and say how many developers are on vacation, that is, give us a number. And some will remain silent; if no one is on vacation, we will get an empty string.

Here, the input may have different types. An if statement tests the condition’s value as a Boolean, so we can use numbers, strings, true, false, or variables holding those values directly as conditions.

The main thing is to understand how these values are converted to a Boolean. true and false remain themselves. Of the numbers used here, all except 0 are converted to true, and 0 is converted to false. All strings except the empty string are converted to true; the empty string '' is converted to false. A variable declared without assigning a value contains undefined, which is also converted to false.

if ('some line') {
  // Non-empty string cast to true
  // Condition will be met
};

if ('') {
  // Empty string cast to false
  // Condition will not be met
};

if (123) {
  // Number is cast to true
  // Condition will be met
};

if (0) {
  // 0 is cast to false
  // Condition will not be met
};

Now we can return to Muffin’s new program “Can I start the project?” To verify that the condition is working correctly, we will try to change the value of the onVacation variable.