javascript - JSHint 警告 "Function declared within loop referencing an outer scope variable may lead to confusing semantics"。我怎样才能改进代码？

Question

JSHint 显示错误:“在引用外部范围变量的循环内声明的函数可能会导致语义混淆”。如何改进以下代码以消除警告？

var getPrecedence  = function getPrecedence(operator, operators) {
    var keys = Object.keys(Object(operators));
    for (var i = 0, len = keys.length; i < len; i++) {
        var check = Object.keys(operators[keys[i]]).some(function (item) {
            return item === operator;
    });
    if (check) return operators[keys[i]][operator];
    }
};

Answer 1

你不应该在循环体内使用函数表达式，而是在外面声明它:

function getPrecedence(operator, operators) {
    function isOperator(item) {
//  ^^^^^^^^^^^^^^^^^^^^^^^^^^^
        return item === operator;
    }
    var keys = Object.keys(Object(operators));
    for (var i = 0, len = keys.length; i < len; i++) {
        var check = Object.keys(operators[keys[i]]).some(isOperator);
//                                                       ^^^^^^^^^^
        if (check) return operators[keys[i]][operator];
    }
}

当然，整个事情可以通过使用 includes 来简化。而不是 some , 和 find 而不是循环:

function getPrecedence(operator, operators) {
    var keys = Object.keys(Object(operators));
    var opkey = keys.find(key =>
        Object.keys(operators[key]).includes(operator)
    );
    if (opkey) return operators[opkey][operator];
}

最后，Object.keys(…).includes(…)可以简化为operator <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/in" rel="noreferrer noopener nofollow">in</a> operators[key] .