Fundamentalsbeginner
Template Literals and Tagged Templates
Backtick strings that support multi-line text and expression interpolation, plus the tagged template function pattern.
Template literals, introduced in ES6, replaced a lot of clunky string-concatenation code with a cleaner syntax using backticks instead of quotes. They are a small feature on the surface but interviewers use them to check whether you're comfortable with modern JS syntax and understand the less obvious 'tagged template' variant.
Template literals are like mail-merge in a word processor: you write a letter with placeholders (`${name}`), and the interpolation engine fills them in — a tagged template is what happens if you hand that merged letter to an editor first, who can reformat or redact parts before it's sent.
Key Concepts
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Inside backticks, ${expression} interpolates any JavaScript expression directly into the string, evaluated and converted to a string at runtime — no more chains of + concatenation. Template literals also natively support multi-line strings; a literal newline inside the backticks becomes a newline in the resulting string, which previously required escape characters or array-joining tricks.
${expression}+
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The more advanced form is the tagged template: prefixing a template literal with a function name (tag\Hello ${name}\`) calls that function with an array of the literal string pieces and the interpolated values as separate arguments, letting you intercept and transform the output before it becomes a final string. This is how libraries like styled-components` implement CSS-in-JS, and how safe HTML-escaping template tags prevent injection by processing interpolated values before they're inserted.
tag\) calls that function with an array of the literal string pieces and the interpolated values as separate arguments, letting you intercept and transform the output before it becomes a final string. This is how libraries like
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Most day-to-day usage never goes beyond basic interpolation, but understanding tagged templates explains 'magic' library APIs that otherwise look like plain string syntax, and it's a common 'do you know this exists' interview checkpoint.