Lodash _.templateSettings.evaluate

Beginner
5 min read
Updated: Nov 2026
5 examples
Template
Decorative image with the word EVALUATE

Definition

A RegExp that marks tags whose contents are executed as JavaScript by _.template() (default <% ... %>). Part of Lodash Properties (stable in 4.x — not deprecated). Warning: never compile untrusted template strings — evaluate tags run code; Lodash plans to remove _.template in v5.

Set the property globally, or override it per call with options passed to _.template().

Syntax

Use _.templateSettings.evaluate. Start with this line.

Lodash
_.templateSettings.evaluate
CallWhat it does
_.templateSettings.evaluatePrimary setting.
_.templateSettings.evaluate = /.../gAssign a custom RegExp or value before compiling.

Prefer the full Lodash build when using _.template() and _.templateSettings.

Library declarations
Lodash
_.templateSettings.evaluate

Parameters

ParameterDescription
_.templateSettings.evaluateOptional. (RegExp) Pattern for JS logic tags
Default patternOptional. (RegExp) /<%([\s\S]+?)%>/g
Capture groupRequired. JavaScript source inside the tag

Return Value

Return ValueDescription
*RegExp (with a capturing group)

Lodash Examples

Example 1 — Official: Evaluate + Escape List

Evaluate tags run the loop; escape tags print each item safely.

Lodash
var compiled = _.template(
  '<% _.forEach(users, function(user) { %>' +
    '<li><%- user %></li>' +
  '<% }); %>'
);
compiled({ 'users': ['fred', 'barney'] });
// → '<li>fred</li><li>barney</li>'
Try It Yourself

How It Works

  1. Evaluate. <% _.forEach(...) %> starts the loop.
  2. Imports. _ comes from templateSettings.imports.
  3. Escape. <%- user %> prints each name HTML-escaped.
  4. Close. <% }); %> ends the callback and call.

Example 2 — if / else Branches

Evaluate tags choose which markup path to render.

Lodash
var tpl = _.template(
  '<% if (ok) { %>yes<% } else { %>no<% } %>'
);
tpl({ ok: true });
// → 'yes'

tpl({ ok: false });
// → 'no'
Try It Yourself

How It Works

  1. Condition. <% if (ok) { %> opens a branch.
  2. Static text. yes / no sit outside tags as literal output.
  3. Else. The second evaluate block handles the false path.
  4. Data. ok comes from the object passed to the compiled function.

Example 3 — Evaluate Does Not Auto-Print

An expression inside evaluate is run, but its return value is not inserted.

Lodash
_.template('A<% 1 + 2 %>B')({});
// → 'AB'   (no "3")

_.template('A<%= 1 + 2 %>B')({});
// → 'A3B'  (interpolate prints)
Try It Yourself

How It Works

  1. Evaluate. 1 + 2 runs but does not write to the output buffer.
  2. Literals. Only A and B remain → AB.
  3. Interpolate. <%= 1 + 2 %> inserts 3.
  4. Rule. Logic in evaluate; values in escape/interpolate.

Example 4 — Custom Evaluate Delimiters

Override the RegExp per compile for alternate logic tags.

Lodash
var compiled = _.template(
  '{% if (ok) { %}Y{% } else { %}N{% } %}',
  { evaluate: /{%([\s\S]+?)%}/g }
);
compiled({ ok: true });
// → 'Y'
Try It Yourself

How It Works

  1. Option. Per-call evaluate overrides the global setting.
  2. Pattern. Must include one capturing group for the JS source.
  3. Tags. {% ... %} now acts like <% ... %>.
  4. Safer scope. Prefer options over mutating templateSettings globally.

Example 5 — Loop With a Counter

Use evaluate tags to track index while printing rows.

Lodash
var compiled = _.template(
  '<% var i = 0; _.forEach(items, function(item) { i++; %>' +
    '<%- i %>. <%- item %>; ' +
  '<% }); %>'
);
compiled({ items: ['a', 'b', 'c'] });
// → '1. a; 2. b; 3. c; '
Try It Yourself

How It Works

  1. Setup. Evaluate block initializes i and starts forEach.
  2. Increment. i++ runs each iteration inside evaluate.
  3. Print. Escape tags output the counter and item text.
  4. Close. Final evaluate block ends the callback.
Compatibility

Browser & Runtime Support

_.templateSettings.evaluate ships with Lodash full builds (stable in 4.x). It configures _.template, which runs anywhere Lodash runs — modern browsers (CDN or bundle) and Node.js / Bun / Deno with npm install lodash.

✓ Stable · Lodash 4.x · Warning: template security

_.templateSettings.evaluate

Available on the [email protected] namespace. Works in evergreen browsers and current Node LTS when Lodash is installed. Treat _.template as legacy for untrusted template source.

100% With Lodash 4.x
Google Chrome Supported · Desktop & Mobile
Full support
Mozilla Firefox Supported · Desktop & Mobile
Full support
Apple Safari Supported · macOS & iOS
Full support
Microsoft Edge Supported · Chromium
Full support
Internet Explorer No native support · Use a polyfill
Polyfill
Opera Supported · Modern versions
Full support
Samsung Internet Supported · Android
Full support
Bun Supported · JavaScript runtime
Supported
Deno Supported · JavaScript runtime
Supported
Node.js Supported · Server runtime
Supported
Android WebView Supported · Modern WebView
Full support
.evaluate Lodash 4.x

Bottom line: Use evaluate tags for loops and conditionals; print with escape/interpolate tags. Prefer per-call { evaluate } options over global mutation. Never compile untrusted template strings.

Frequently Asked Questions

It is a RegExp that tells _.template() which tags contain JavaScript to execute. The default matches <\x25 ... \x25> logic tags.
A RegExp. Lodash uses it at compile time to find control-flow blocks. Do not assign a callback to evaluate.
Interpolate tags (<\x25= \x25>) evaluate an expression and insert the result. Evaluate tags (<\x25 \x25>) run JavaScript for logic — loops, if/else, setup — without automatically printing a value.
Pair evaluate tags for the loop with escape or interpolate tags for output, e.g. <\x25 _.forEach(users, function(user) { \x25><li><\x25- user \x25></li><\x25 }); \x25>.
Yes. Pass { evaluate: /.../g } to _.template(string, options) to override _.templateSettings.evaluate for that compile only.
No. Compiling untrusted templates can execute code. Use only developer-controlled templates. Lodash plans to remove _.template in v5.

Next: _.templateSettings.imports

Inject free variables (like _) into compiled templates.

.imports tutorial →

About the author

Mari Selvan M P
Mari Selvan M P 🔗

Developer, cloud engineer, and technical writer

  • Experience 12 years building web and cloud systems
  • Focus Full Stack Development, AWS, and Developer Education

I write practical tutorials so students and working developers can learn by doing—from databases and APIs to deployment on AWS.

AWS Certified Developer – Associate (Credly)

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Lodash _.templateSettings.escape Lodash _.templateSettings.imports