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typeof-not-undefined
(version: 0)
Comparing performance of:
typeof vs eq
Created:
3 years ago
by:
Guest
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Tests:
typeof
const a = {a:true,b:1,c:"x"}; typeof a !== 'undefined'
eq
const a = {a:true,b:1,c:"x"}; a !== undefined
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Suite status:
<idle, ready to run>
Run tests (2)
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Test case name
Result
typeof
eq
Fastest:
N/A
Slowest:
N/A
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Autogenerated LLM Summary
(model
llama3.2:3b
, generated one year ago):
Let's dive into the world of JavaScript microbenchmarks. **What is being tested?** The provided JSON represents a benchmark that tests two different approaches to compare the values of `typeof` and `!== undefined`. The test case uses a simple object literal with four properties: `a`, `b`, `c`, and an empty string. The objective is to determine whether the value returned by `typeof` for property `a` is `'undefined'`. **Options compared** There are two options being compared: 1. **`typeof`**: Returns a string indicating the type of the variable. In this case, it will return `'object'`, because `a` is an object literal. 2. **`!== undefined`**: Checks whether the value is not equal to `undefined`. Since `a` is an object literal, its properties are accessed using dot notation (`a.b.c`), but for simplicity, we're comparing the value of `a` directly. **Pros and Cons** * **`typeof`:** + Pros: - More concise and expressive. - Can be useful when you want to get a string representation of the type (e.g., `'object'`, `'number'`, etc.). + Cons: - May not always return what you expect, especially for complex data structures or functions. * **`!== undefined`**: + Pros: - More straightforward and easy to understand. - Works well with simple values. + Cons: - Less concise than `typeof`. - Can be slower, since it involves a value comparison. **Library** There is no explicit library mentioned in the provided JSON. However, it's worth noting that some JavaScript engines or frameworks might provide additional features or optimizations for specific use cases, such as comparing values using `===` instead of `!==`. **Special JS feature or syntax** The test case uses the dot notation (`a.b.c`) to access properties of an object literal, which is a standard JavaScript feature. However, it's not explicitly mentioned in the JSON. **Other alternatives** There are several other ways to compare values in JavaScript, including: * `===` and `!==`: Compare two values using strict equality (value and type). * `==` and `!=`: Compare two values using loose equality (value only, ignoring type). * `instanceof`: Check if an object is an instance of a constructor. * `Object.prototype.toString.call()`: Get the type of an object as a string. These alternatives have their own pros and cons, which are discussed in various JavaScript documentation sources.
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typeof number vs not typeof undefined vs undefined
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