WTF is a Ternary Statement

TL;DR The ternary (pronounced "turn hairy" if you said it really fast) statement is just an if-else block made with symbols.

Let's use an example.

Say you want to shorten some text that is longer than 40 characters. First we'll need to check if the text has more than 40 characters. If it does, we'll take the first 40 and drop the rest. Otherwise we'll just keep the original text. Let's make a function that will do exactly that.

function shortenLongerThan40(text) {
if (text.length > 40) {
// return a substring starting from the 0 index up to the 40th character
return text.substr(0, 40);
} else {
// if it is shorter than 40, we just give back the original text
return text;
}
}

Here I just checked if the string has more than 40 characters text.length > 40 and used the substr method to take care of shortening the string. The ternary operator can be used here to make the code even shorter.

function shortenLongerThan40(text) {
return text.length > 40 ? text.substr(0, 40) : text;
}

Both functions will give you the same output, but the ternary operator let's you do it in one line. So how does it work?

The trick to understanding the ternary operator is to imagine it as just an if-else block. Let's break down the if-else block from the first example, and compare it to the second.

function shortenLongerThan40(text) {
// condition
if (text.length > 40) {
// what to return if true
return text.substr(0, 40);
} else {
// what to return if false
return text;
}
}

The if-else block has 3 parts:

  • The condition
  • What to do when it's true
  • What to do when it's not

The same is true for the ternary operator except we just add in some symbols to separate the 3 parts.

function shortenLongerThan40(text) {
// condition ? if it's true : if it's false
return text.length > 40 ? text.substr(0, 40) : text;
}

Now we are immediately returning a value based on the text length. When using the ternary, the condition goes before the ? and the value you want to return if it's true comes after. Everything after the : is the else statement.

Let's use another example to drive this home. Say we want to make a function that simulates flipping a coin. Some logical steps to accomplish could be:

  1. Get a random number between 0 and 1
  2. Check if the number is less than 0.5
  3. If it's true, return "Heads", otherwise return "Tails"

Let's code out this logic using an if-else block and a ternary statement. First, here's the if-else version:

function simulateCoinToss() {
if (Math.random < 0.5) {
return "Heads";
} else {
return "Tails";
}
}

Now compare that to a function that gives the same output using the ternary operator:

function simulateCoinToss() {
return Math.random() < 0.5 ? "Heads" : "Tails";
}

Both get the job done, but the ternary statement provides a concise way to accomplish the same goal.

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