Native JS achieve every () method

Definition and Usage

every () method for detecting whether all of the array elements meet the specified criteria (provided by the function).

every () method uses the specified function of all elements in the array detector:

• If the array has a detected element is not satisfied, then the whole expression evaluates  to false  , and the remaining elements will not be detected.
• If all elements conditions are met, it returns true.

Note:  Every () will not be an empty array detection.

Note:  Every () does not alter the original array.

grammar

array.every(function(currentValue,index,arr), thisValue)

Parameter Description

parameter	description
function(currentValue, index,arr)	have to. Function, each element of the array will perform this function function parameters: parameter description currentValue have to. The current value of the element index Optional. The current index value of the element arr Optional. Current array object element belongs
thisValue	Optional. Examples of the use of callback object, passed to the function, as the value of "this". If omitted thisValue, "this" value "undefined"

achieve

// 实现every
Array.prototype.every = function(fn, value){
    if (typeof fn !== "function") {
        return false;
    }
    var arr = this;
    for (var i = 0; i < arr.length; i++) {
        var result = fn.call(value, arr[i], i, arr);
        if (!result) return false;
    }
    return true;
}

test

var arr = [2,23,4,2,4,2,2];
    console.log(arr.every(function(item, index, arr){
    return item >= 0;
}));