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Test all array items for equality

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The .every method tests if all array elements pass a provided predicate test.

To test all objects for equality, you can use the following code snippets. 

[1, 2, 1].every(function(item, i, list) { return item === list[0]; }); // false
[1, 1, 1].every(function(item, i, list) { return item === list[0]; }); // true

[1, 1, 1].every((item, i, list) => item === list[0]); // true

The following code snippets test for property equality 

let data = [
  { name: "alice", id: 111 },
  { name: "alice", id: 222 }
];

data.every(function(item, i, list) { return item === list[0]; }); // false
data.every(function(item, i, list) { return item.name === list[0].name; }); // true

data.every((item, i, list) => item.name === list[0].name); // true
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Arrays:
* Syntax
* Remarks
* Converting Array-like Objects to Arrays
* Reducing values
* Mapping values
* Filtering Object Arrays
* Sorting Arrays
* Iteration
* Removing duplicate elements
* Destructuring an array
* Array comparison
* Reversing arrays
* Concatenating Arrays
* Shallow cloning an array
* Merge two array as key value pair
* Array spread rest
* Finding the minimum or maximum element
* Removing items from an array
* Filtering values
* Standard array initialization
* Removing all elements
* Searching an Array
* Convert a String to an Array
* Joining array elements in a string
* Removing / adding elements using splice
* The entries() method
* Remove value from array
* Logical connective of values
* Flattening Arrays
* Object keys and values to array
* Append / prepend items to array
* Checking if an object is an array
* Sorting multidimensional array
* Insert an item into an array at a specific index
* Test all array items for equality
* Copy part of an array with slice()
* Using map to reformat objects in an array
Table Of Contents
0 Getting started
1 Comments
2 Basic data types
3 Built-in constants
4 Variables
5 Declarations and assignments
6 Reserved keywords
7 Data types in JavaScript
8 Strings
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10 Template Literals
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50 Web Worker
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57 execCommand and contenteditable
58 Performance Tips
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72 Functional JavaScript
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81 Automatic Semicolon Insertion
82 IndexedDB
83 Anti-patterns
84 Navigator Object
85 Modularization techniques
86 Proxy
87 Same origin policy, cross-origin communication
88 postMessage and MessageEvent
89 WeakMap
90 WeakSet
91 Behaviroal Design Patterns
92 Server-sent events
93 Async iterators
94 Namespacing
95 Evaluating JavaScript
96 Memory efficiency
97 How to make iterator usable inside async callback function
98 Context this
99 Setters and getters
100 Vibration API
101 Fluent API
102 Tilde
103 Security issues
104 Get and set CSS custom variables
105 Contributors