Template Strings, String interpolation & multi-line Typescript

Template strings (or Template literals ) in Typescript are multi-line string literals allowing string interpolation. String interpolation allows us to include embedded expressions as part of the string. You can also use multi-line strings, basic string formatting & tagged templates with Template strings. They are part of ES2016/ES6 specification. Template strings are also called as template literals. In this tutorial, we will learn the Template strings (or Literals) syntax and how to use it in Multiline Strings & string interpolation. We will also learn how to nest expressions and how to Escaping template literals using the backslash (\)

Template Strings Syntax

The Syntax of template literals as shown below

1. The expression must be specified inside dollar sign and curly braces (${expression})
2. We must enclose them in template literal syntax or back-tick.
3. You must enable the "target": "es6", or "target": "es2015", in the tsconfig.json file
4. Template literals always produce strings

Multiline strings

The following is an example of creating a multiline string. Just hit enter and continue in the next line. The \n character is automatically gets inserted in the string.

Example

The multiline strings without back-quote are created by inserting a \n newline character (LF).

As we said earlier, the /n (LF) character is inserted when you use the template strings. Hence the following code is true.

String Interpolation

string interpolation (expression Interpolation) is the process of evaluating a string literal containing one or more expressions. It evaluates the expression and coerces the result into a string. The result is then is replaced in the original string.

Example

In the following example, $(palyerName) is the expression. It is evaluated first and the resulting value “Sachin Tendulkar” is replaced at its place in the final string.

Multiple Expressions

Using Expressions

The following example shows that you can use any expressions inside the template string. It uses the arithmetic expression ${a+b}

The following example uses the ternary conditional operator(?) in the template string.

String Interpolation Nesting Expressions

You can nest expressions

Escaping in template strings

The backslash \ is used for escaping inside template literals. It enables you to mention backticks and ${ inside template literals:

Tagged Templates

Another use of the Template string is in Tagged Templates. We can tag a function to a template string. This gives an opportunity to parse the template literals and control how it gets converts into a string.

You can read more about it from Tagged Templates in the next tutorial.

Reference

Template literals

Summary

In this tutorial, we learned about Template Strings. They allow us to put embedded expressions inside a string using the syntax ${expression}. We can use any expressions that return in a string. We can also use nested expressions also.