將數組[NaN ,1,21,32,NaN,41,5]裏面的NaN成員剔除（複用underscore.js的filter方法）

時間 2019-11-18

標籤數組 nan 裏面成員剔除 underscore.js underscore filter 方法欄目 JavaScript 简体版

原文原文鏈接

<!DOCTYPE HTML>
<html>
<body>
</body>
<script type="text/javascript">
(function(root) {
    var push = Array.prototype.push;
    var _ = function(obj) {
        if (obj instanceof _) {
            return obj;
        }

        if (!(this instanceof _)) {
            return new _(obj);
        }
        this._wrapped = obj;
    }
    var cb = function(iteratee, context, count) {
        if (iteratee == null) {
            return _.identity;
        }

        if (_.isFunction(iteratee)) {
            return optimizeCb(iteratee, context, count);
        }
    }
    //optimizeCb優化迭代器
    var optimizeCb = function(func, context, count) {
        if (context == void 0) {
            return func;
        }

        switch (count == null ? 3 : count) {
            case 1:
                return function(value) {
                    return func.call(context, value);
                };
            case 3:
                return function(value, index, obj) {
                    return func.call(context, value, index, obj);
                };
            case 4:
                return function(memo, value, index, obj) {
                    return func.call(context, memo, value, index, obj);
                };
        }
    }    
        _.isArray = function(array) {
        return toString.call(array) === "[object Array]";
    }
        _.each = function(target, callback) {
        var key, i = 0;
        if (_.isArray(target)) {
            var length = target.length;
            for (; i < length; i++) {
                callback.call(target, target[i], i);
            }
        } else {
            for (key in target) {
                callback.call(target, key, target[key]);
            }
        }

    }
    _.each(["Function", "String", "Object", "Number", "Boolean", "Arguments"], function(name) {
        _["is" + name] = function(obj) {
            return toString.call(obj) === "[object " + name + "]";
        }
    });
    //predicate  真值檢測(重點: 返回值)
    _.filter = function(obj, predicate, context) {
        var results = [];
        predicate = cb(predicate, context);
        _.each(obj, function(value, index, list) {
            if (predicate(value, index, list)) results.push(value);
        });
        return results;
    };

    root._ = _;
})(this);
/*思路：定義一個underscore的filter函數，由於只有NaN是不等於自身的，因此真值檢測中設置返回等於自身的元素
*/
var arr = [NaN ,1,21,32,NaN,41,5];
var bb = _.filter(arr,function(num) {
                return num  === num;
            });
console.log(bb);//[1, 21, 32, 41, 5]
</script>
</html>

相關標籤/搜索

每日一句

每一个你不满意的现在，都有一个你没有努力的曾经。