JavaScript Feature Reference: keys() Method On Arrays Web Browser Support Test

1. Introduction

In this web page there are two web browser JavaScript feature support tests; 1.) a feature implementation test, and 2.) a feature capability test. First, the implementation test is run. The implementation test determines if the web browser recognizes the JavaScript keys() method on arrays. The implementation test is a simple test for the presence of web browser support, and a definitive test for the absence of web browser support. If the web browser does not recognize the JavaScript keys() method on arrays, the testing is stopped and the implementation test reports: Fail (no support): The web browser does not recognize the JavaScript keys() method on arrays. The web browser does not support the JavaScript keys() method on arrays.

If the web browser recognizes the JavaScript keys() method on arrays, the capability test is run. The capability test determines if the web browser's implementation of the JavaScript keys() method on arrays includes support for at least one keys() method on arrays capability. The capability test is a more definitive, albeit not an all inclusive, test for the presence of web browser support. If the web browser's implementation of the JavaScript keys() method on arrays includes support for the tested capability, the capability test reports: Pass (at least partial/possibly full support): The web browser recognizes the JavaScript keys() method on arrays, and supports at least one keys() method on arrays capability. The web browser at least partially/possibly fully supports the JavaScript keys() method on arrays. Positive determination of full web browser support is beyond the scope of this test. If the web browser's implementation of the JavaScript keys() method on arrays does not include support for the tested capability, the capability test reports: Pass/Fail (partial support): The web browser recognizes the JavaScript keys() method on arrays, but does not support at least one keys() method on arrays capability. The web browser partially supports the JavaScript keys() method on arrays.

The web browser support test source code is shown in Section 2.1. The web browser support test source code is run in Section 2.2, which shows the web browser support test result.

1.1. keys() Method On Arrays Web Browser Support

• Pass (at least partial/possibly full support): ED12+, FF28+, CH38+, OP25+.
• Fail (no support): IE11-, SF5.1.7-.

1.2. Abbreviations

• IE = Internet Explorer.
• ED = Edge Legacy 12 - 18 (EdgeHTML based) and Edge 79+ (Chromium based).
• FF = Firefox.
• SF = Safari.
• CH = Chrome.
• OP = Opera.

2. keys() Method On Arrays Web Browser Support Test

2.1. Web Browser Support Test Source Code

<p id='testId'><b>Fail</b> (no support): The web browser does not recognize the JavaScript <code>keys()</code> method on arrays. The web browser does not support the JavaScript <code>keys()</code> method on arrays.</p><!-- Hard code Fail because web browser no support error stops JavaScript execution. -->

<script>
var arrayViaArrayConstructor = new Array();
arrayViaArrayConstructor[0] = "a";
arrayViaArrayConstructor[1] = "b";
arrayViaArrayConstructor[2] = "c";
var arrayLiteral = ["d", "e", "f"];
// Get references to array built-in array iterator object called by keys() method. NOTE: keys() method can be considered a generator function. Call keys() generator functions. Each call returns a Generator object which inherits prototype from Object (window.Generator property does not exist) and is an iterator. Generator object has next() method property. Called by keys(), array iterator object next() method return object value property is set to array element numeric index.
var arrayViaArrayConstructorIteratorKeys = arrayViaArrayConstructor.keys();
var arrayLiteralIteratorKeys = arrayLiteral.keys();
var arrayViaArrayConstructorIteratorKeysNextValues = [];
var arrayLiteralIteratorKeysNextValues = [];
for (var i = 0; i < arrayViaArrayConstructor.length; i++){ // Identical to for (var key of arrayViaArrayConstructor.keys()){console.log(key);}. 1.) 0, 2.) 1, 3.) 2.
 arrayViaArrayConstructorIteratorKeysNextValues[i] = arrayViaArrayConstructorIteratorKeys.next().value;
}
for (var i = 0; i < arrayLiteral.length; i++){ // Identical to for (var key of arrayLiteral.keys()){console.log(key);}. 1.) 0, 2.) 1, 3.) 2.
 arrayLiteralIteratorKeysNextValues[i] = arrayLiteralIteratorKeys.next().value;
}
if (arrayViaArrayConstructor.keys && arrayLiteral.keys){
 var element = document.getElementById("testId");
 if ((typeof arrayViaArrayConstructorIteratorKeys === "object") && arrayViaArrayConstructorIteratorKeys instanceof Object && Object.prototype.isPrototypeOf(arrayViaArrayConstructorIteratorKeys) && (typeof arrayViaArrayConstructorIteratorKeysNextValues[0] === "number") && (arrayViaArrayConstructorIteratorKeysNextValues[0] === 0) && (arrayViaArrayConstructorIteratorKeysNextValues[1] === 1) && (arrayViaArrayConstructorIteratorKeysNextValues[2] === 2) && (typeof arrayLiteralIteratorKeys === "object") && arrayLiteralIteratorKeys instanceof Object && Object.prototype.isPrototypeOf(arrayLiteralIteratorKeys) && (typeof arrayLiteralIteratorKeysNextValues[0] === "number") && (arrayLiteralIteratorKeysNextValues[0] === 0) && (arrayLiteralIteratorKeysNextValues[1] === 1) && (arrayLiteralIteratorKeysNextValues[2] === 2)){
  element.innerHTML = "<b>Pass</b> (at least partial/possibly full support): The web browser recognizes the JavaScript <code>keys()</code> method on arrays, and supports at least one <code>keys()</code> method on arrays capability. The web browser at least partially/possibly fully supports the JavaScript <code>keys()</code> method on arrays. Positive determination of full web browser support is beyond the scope of this test.";
 } else {
  element.innerHTML = "<b>Pass/Fail</b> (partial support): The web browser recognizes the JavaScript <code>keys()</code> method on arrays, but does not support at least one <code>keys()</code> method on arrays capability. The web browser partially supports the JavaScript <code>keys()</code> method on arrays.";
 }
}
</script>

2.2. Web Browser Support Test Result

Fail (no support): The web browser does not recognize the JavaScript keys() method on arrays. The web browser does not support the JavaScript keys() method on arrays.

3. Resources And Additional Information

• JavaScript Feature Reference (learnwebcoding.com)