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javascript/snippets/deep-freeze.md

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+---
+title: Deep freeze object
+type: snippet
+tags: [object,recursion]
+cover: frozen-globe
+dateModified: 2020-10-19T18:51:03+03:00
+---
+
+Deep freezes an object.
+
+- Use `Object.keys()` to get all the properties of the passed object, `Array.prototype.forEach()` to iterate over them.
+- Call `Object.freeze()` recursively on all properties, applying `deepFreeze()` as necessary.
+- Finally, use `Object.freeze()` to freeze the given object.
+
+```js
+const deepFreeze = obj => {
+  Object.keys(obj).forEach(prop => {
+    if (typeof obj[prop] === 'object') deepFreeze(obj[prop]);
+  });
+  return Object.freeze(obj);
+};
+```
+
+```js
+'use strict';
+
+const val = deepFreeze([1, [2, 3]]);
+
+val[0] = 3; // not allowed
+val[1][0] = 4; // not allowed as well
+```