Using strict mode in the Node.js REPL

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If you want to use strict mode [1] in the Node.js REPL, you have two options.


Option 1. Start the REPL as usual, wrap your code in an IIFE [2]:


    > (function () { 'use strict'; 'abc'.length = 1 }());
    TypeError: Cannot assign to read only property 'length'

(Assigning to a read-only property fails silently in sloppy mode.)


Option 2. Use the Node.js command line option --use_strict:


    node --use_strict

Afterwards, everything you write in the REPL is interpreted in strict mode:

    > 'abc'.length = 1
    TypeError: Cannot assign to read only property 'length'


References:


  1. JavaScript’s strict mode: a summary

  2. JavaScript variable scoping and its pitfalls


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