<h2>Generated with GPT4
(Refer editorial solution for explanation with ECMAScript Spec)</h2>
In JavaScript, the behavior of the + and - operators can sometimes be counter-intuitive when applied to non-number types. This is due to type coercion, where JavaScript automatically converts one or more values to a different type. In this article, we will discuss a simple mnemonic that will help you remember how type coercion works with the + and - operators.
The Mnemonic:
<ul>
<li>If there is a + operator, convert the objects to strings and try to evaluate the expression (string concatenation is preferred with the + operator).</li>
<li>If there is a - operator, convert the objects to numbers and try to evaluate the expression (subtraction with numbers is preferred).</li>
</ul>
Understanding the + Operator:
With the + operator, JavaScript tries to do string concatenation if one of the operands is a string. When objects are involved, they are converted to their string representations. For example, an object is converted to "[object Object]" and an array is converted to a string with comma-separated elements (or an empty string if it's empty).
<pre><code>console.log([] + []); // "" (empty string)
console.log([] + {}); // "[object Object]" (array converts to empty string)
console.log({} + {}); // "[object Object][object Object]" (both objects convert to strings)
console.log([1, 2, 3] + {}); // "1,2,3[object Object]"
</code></pre>
Understanding the - Operator:
With the - operator, JavaScript attempts to convert the values into numbers to perform subtraction. Empty arrays are coerced to 0, while non-empty arrays and objects have a numeric value of NaN (unless the array has one number inside, then it's coerced to that number).
<pre><code>console.log([] - 1); // -1 (empty array is 0)
console.log([2] - 1); // 1 (single-element array is 2)
console.log([1, 2, 3] - 1); // NaN (multi-element array can't convert to number)
console.log({} - 1); // NaN (object can't convert to number)
</code></pre>
Caveats and Complications:
There are some additional nuances. For example, the expression {} + {} can be tricky because {} can also be interpreted as a block, not just an object literal. Context and placement matter.

Understanding Type Coercion with '+' and '-' in JavaScript

What does the code snippet to the right output by console.log?…