Is comparing strings in JavaScript as efficient as comparing numbers?

Question

Is comparing strings in JavaScript as efficient as comparing numbers?

Considering creating a JavaScript enum library involves deciding how to store the values, I'm at a crossroads. Should I opt for speed in comparison or prioritize readability during debugging by using strings or numbers? While objects are an option too, that leads to another question.

For instance:

// Avoiding this due to lack of readability when debugging
var Planets = {Earth:0, Mars:1, Venus: 2}

// Preferring this for clarity with Planets.Earth returning a readable value ("Earth")
var Planets = {Earth: 'Earth', Mars: 'Mars'}

Concerns arise when comparing them with if (myPlanet === Planet.Earth). Could string comparison potentially slow down performance, especially in loops? The ECMAScript specification suggests so.

If Type(x) is String, then return true if x and y are exactly the same sequence of characters (same length and same characters in corresponding positions); otherwise, return false.

In testing, both string and number comparisons seem to take equal time, as shown here: http://jsperf.com/string-comparison-versus-number-comparison/2. It doesn't appear to scan the entire string.

While this may be a minute optimization, my query remains: does string equality comparison utilize pointers, making it as efficient as number equality comparison?

javascript string performance enums

Answer 1

Answer №1

When it comes to comparing strings, the speed can vary depending on the implementation and values being compared. It could be just as fast or much slower.

The ECMAScript specification focuses on describing the semantics rather than the actual implementation. To truly determine the performance of string comparison, creating a relevant benchmark and running it on a specific implementation is necessary.

In some cases, the effects of string interning in a particular implementation are noticeable. This means that all string values from literals can be interned into a pool, allowing for simple comparisons like implIdentityEq("foo", "foo") to return true with only one string object needed.

If string interning is employed, the initial check for implStringEq could involve evaluating implIdentityEq(x,y). If true, the comparison is quick and easy. Otherwise, a character-wise comparison would follow, which takes longer.

There are various optimizations beyond string interning that modern JavaScript implementations utilize for better performance. The jsperf created for an "intern breaker" demonstrates these optimizations in action.

Interned strings lead to performance comparable to testing for identity, making it faster than character-by-character comparisons.
While IE10 prioritizes fast-fail length checks over object-identity for string comparisons, Chrome and Firefox handle different interned strings efficiently as well.
Even for small strings, interning significantly boosts performance. IE10 lacks this optimization, despite having efficient string comparison implementation.
String comparisons stop at the first differing character, even when comparing equal-length long strings.

Common JavaScript implementations do use string interning for literal strings and constants, although the specifics may vary between implementations.
Firefox's JS_InternString feature demonstrates how string interning works within the browser implementation.

Answer 2

When it comes to comparing strings, the speed can vary depending on the implementation and values being compared. It could be just as fast or much slower.

The ECMAScript specification focuses on describing the semantics rather than the actual implementation. To truly determine the performance of string comparison, creating a relevant benchmark and running it on a specific implementation is necessary.

In some cases, the effects of string interning in a particular implementation are noticeable. This means that all string values from literals can be interned into a pool, allowing for simple comparisons like implIdentityEq("foo", "foo") to return true with only one string object needed.

If string interning is employed, the initial check for implStringEq could involve evaluating implIdentityEq(x,y). If true, the comparison is quick and easy. Otherwise, a character-wise comparison would follow, which takes longer.

There are various optimizations beyond string interning that modern JavaScript implementations utilize for better performance. The jsperf created for an "intern breaker" demonstrates these optimizations in action.

Interned strings lead to performance comparable to testing for identity, making it faster than character-by-character comparisons.
While IE10 prioritizes fast-fail length checks over object-identity for string comparisons, Chrome and Firefox handle different interned strings efficiently as well.
Even for small strings, interning significantly boosts performance. IE10 lacks this optimization, despite having efficient string comparison implementation.
String comparisons stop at the first differing character, even when comparing equal-length long strings.

Common JavaScript implementations do use string interning for literal strings and constants, although the specifics may vary between implementations.
Firefox's JS_InternString feature demonstrates how string interning works within the browser implementation.

Answer 3

Answer №2

There are instances where comparing dynamically created strings can significantly slow down string comparison processes.

In both Chrome and IE, the following code snippet runs 77% slower compared to other tests:

var StringEarth = 'Ear' + 'th';
for (var i = 0; i < ITERATIONS; i++) {
  x = StringPlanets.Venus === StringEarth;
}

The flaw in the previously mentioned tests lies in the fact that they are based on literal string comparisons. It appears that JavaScript is optimized to compare string literals efficiently by testing memory pointers. This optimization becomes evident when comparing dynamically generated strings. My assumption is that strings from the literal string pool are marked for address-only comparison.

It's important to note that Firefox shows consistent speed in string comparison, regardless of whether the strings are dynamic or literal.

Conclusion: Different browsers may handle string comparison differently, resulting in variations in speed.

Answer 4

There are instances where comparing dynamically created strings can significantly slow down string comparison processes.

In both Chrome and IE, the following code snippet runs 77% slower compared to other tests:

var StringEarth = 'Ear' + 'th';
for (var i = 0; i < ITERATIONS; i++) {
  x = StringPlanets.Venus === StringEarth;
}

The flaw in the previously mentioned tests lies in the fact that they are based on literal string comparisons. It appears that JavaScript is optimized to compare string literals efficiently by testing memory pointers. This optimization becomes evident when comparing dynamically generated strings. My assumption is that strings from the literal string pool are marked for address-only comparison.

It's important to note that Firefox shows consistent speed in string comparison, regardless of whether the strings are dynamic or literal.

Conclusion: Different browsers may handle string comparison differently, resulting in variations in speed.

Answer 5

Answer №3

String interning, which involves turning a string with a specific value into a unique reference or a symbol that can be compared in constant time, typically requires O(n) time as it needs to examine all characters within the string.

The efficiency of string interning depends on how many comparisons are needed for amortization.

An optimizer can optimize static expressions that build up strings and intern them once for more efficient comparison.

Comparisons involving interned strings, such as those used in enums mapped to integers, are often done in O(1) time.

The most costly comparison cases occur when one operand is a dynamic string, making equality comparisons require at least O(n) time.

When aiming to create something similar to an enum in another language, it's important to ensure that string interning is only done in a few key locations. Different browsers may have varying implementations, complicating matters, especially in older versions like IE10.

If string interning is not available, using the integer version of an enum implementation can result in O(1) complexity for certain operations, provided that values are set efficiently. For example, setting the value of a variable like myPlanet using an established planet through Planets.value can achieve O(1) time complexity.

Answer 6

String interning, which involves turning a string with a specific value into a unique reference or a symbol that can be compared in constant time, typically requires O(n) time as it needs to examine all characters within the string.

The efficiency of string interning depends on how many comparisons are needed for amortization.

An optimizer can optimize static expressions that build up strings and intern them once for more efficient comparison.

Comparisons involving interned strings, such as those used in enums mapped to integers, are often done in O(1) time.

The most costly comparison cases occur when one operand is a dynamic string, making equality comparisons require at least O(n) time.

When aiming to create something similar to an enum in another language, it's important to ensure that string interning is only done in a few key locations. Different browsers may have varying implementations, complicating matters, especially in older versions like IE10.

If string interning is not available, using the integer version of an enum implementation can result in O(1) complexity for certain operations, provided that values are set efficiently. For example, setting the value of a variable like myPlanet using an established planet through Planets.value can achieve O(1) time complexity.

Is comparing strings in JavaScript as efficient as comparing numbers?

Answer №1

Answer №2

Answer №3

Similar questions

Verify the Ajax submission of a post request prior to transmitting any data

The specified project directory was not detected. Please restart Next.js in your updated directory

Leveraging HTTP/2 in conjunction with angularJS

Is it better to utilize a sizable JavaScript file or opt for a compact one?

Using JQuery to append elements and then locate them with the find method does not produce the expected

What is the best way to utilize "exports" in package.json for TypeScript and nested submodules?

"Maximizing the slider with jCarousel: A guide to enhancing your carousel experience

What causes inability for JavaScript to access a property?

What is the best way to combine relative paths or create distinct identifiers for SVG files located within multiple layers of folders

Extracting the name of the file from the image's web address

Creating a simulation of a ReactJS form tag using TestUtils does not activate the `onSubmit` event

Retrieving selective attributes from Cosmos DB NoSQL using NodeJS/Javascript: Exploring the readAll() method for retrieving specific attributes instead of the entire object

When I attempt to use document.execCommand("copy"), the line break does not get applied

Can getServerSideProps be adjusted to avoid triggering a complete page reload after the first load?

The process of obtaining points through accurate responses using form inputs

In IE8, submitting an Ajax request almost always results in an error being

Storing information in Firebase using React.js

Troubleshooting: 404 Error When Trying to Send Email with AJAX in Wordpress

Each block in Svelte includes a unique shorthand attribute

Error message: Encountered JavaScript heap out-of-memory error during Azure DevOps React Container Production Build