Are arrays some and every es6 methods?

some and every are es6 methods. some() and every() are new methods of the es6 Array object. some() is used to detect whether there are elements that meet the conditions in the array. As long as one of them matches, it will return true; and every() is used to detect all elements of the array. Whether the elements all meet the specified conditions.

The operating environment of this tutorial: Windows 7 system, ECMAScript version 6, Dell G3 computer.

some() and every() are new methods of es6 Array object.

• some() method: detects whether there are elements in the array that meet the conditions

• every() method: detects whether all array elements meet the specifications Condition

es6 some() method

some() method is used to detect whether there is an element in the array that meets the specified condition. It exists (as long as Returns true if there is a match), returns false if it does not exist.

Thinking about it from another angle, some() can also be used to detect whether all the elements in the array do not meet the specified conditions. If they do not meet the specified conditions, it will return false. If one or more elements match, it will return true.

some() The specific usage is as follows:

array.some(callbackfn[, thisArg]);

Parameter description:

• array: required parameter, an array object.

• callbackfn: required parameter, a function that receives up to three parameters. The some() method calls the callbackfn function for each element in the array until callbackfn returns true, or until the end of the array is reached.

• thisArg: Optional parameter, an object that can refer to the this keyword in the callbackfn function. If thisArg is omitted, undefined will be used to return false.

The song() method calls the callbackfn function on each array element in ascending index order until the callbackfn function returns true. If an element is found that causes callbackfn to return true, the some() method returns true immediately. If the callback does not return true for any element, the some() method will return false.

The syntax of the callback function is as follows:

function callbackfn(value, index, array);

Users can use three parameters to declare the callback function. The parameters of the callback function are described below.

• value: The value of the array element.

• index: Numeric index of the array element.

• array: Array object containing the element.

The some() method does not call this callback function for missing elements in the array. In addition to array objects, the some() method can be used by any object that has a length property and has a numerically indexed property name, such as associative arrays, Arguments, etc.

Example: Detect whether the value of the element in the array is an odd number

If the some() method detects an even number, it returns true and prompts that it is not all odd; if no even number is detected, it prompts All are odd numbers.

function f(value, index, ar) {
    if (value % 2 == 0) {
        return true;
    }
}
var a = [1,15,4,10,11,22];
var evens = a.some(f);
if (evens) {
    console.log("不全是奇数。");
} else {
    console.log("全是奇数。");
}

es6 every() method

every() method is used to determine whether all elements of the array meet the specified conditions ;Returns true only when all elements in the array meet the conditions, otherwise returns false.

The specific usage of every() is as follows:

array.every(callbackfn[, thisArg]);

Parameter description:

• ##array: required parameter, an array object.

• callbackfn: required parameter, a function that receives up to three parameters. The every() method calls the callbackfn function for each element in the array until callbackfn returns false, or until the end of the array is reached. (For the syntax of the callback function, please refer to the some() method above)

• thisArg: Optional parameter, which can be used to reference the object of the this keyword in the callbackfn function. If thisArg is omitted, undefined is used as the this value.

If the callbackfn function returns true for all array elements, the return value is true; otherwise, the return value is false. The every() method will return true if the array has no elements.

The every() method calls the callbackfn function once for each array element in ascending order until the callbackfn function returns false. If an element is found that causes callbackfn to return false, the every() method immediately returns false; otherwise, the every() method returns true. The every() method does not call this callback function for missing elements in the array.

In addition to array objects, the every() method can be used by any object that has a length property with its own numerically indexed property name, such as associative array objects, Arguments, and so on.

Example: Check whether the elements in the array are all even numbers and prompt

function f (value, index, ar) {
    if (value % 2 == 0) {
        return true;
    }else {
        return false;
    }
}
var a = [2,4,5,6,8];
if (a.every(f)) {
    console.log("都是偶数");
}else{
    console.log("不全为偶数");
}

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