JavaScript中直接使用==或===比较数组会返回false，因为比较的是引用而非内容。本文指出将数组转为字符串比较存在隐患，并推荐采用StackOverflow上提供的方法，通过扩展Array.prototype.equals实现内容层面的深度比较。
JavaScript数组比较的陷阱与正确方法
今日偶然得知，JavaScript无法通过==或===运算符直接判定两个数组内容是否一致。
alert([]==[]); // false
alert([]===[]); // false上述两段代码执行结果均返回false。
鉴于JavaScript中Array属于对象类型，==或===运算符仅能检测两个对象是否指向同一实例，即是否为同一对象引用。当前JavaScript未提供内置操作符来比对对象内容是否相同。
然而，常规思维常误将数组视为值类型，从而认为其可直接进行比较。
若需验证数组相等性，必须遍历数组元素逐一比对。
网络广泛流传的一种方案是将数组转换为字符串：
JSON.stringify(a1) == JSON.stringify(a2)或者
a1.toString() == a2.toString()不建议采用此方式。
该方式在特定场景下有效，即当两个数组元素顺序一致且均可转换为字符串时确实可行。但此类代码存在风险，例如数字与字符串转换后，“1”（数字）与“1”（字符串）会被判定为相等，易引发调试难题，故不推荐。
StackOverflow上有专家提供了正确方法，此处仅作转载：
// Warn if overriding existing method
if(Array.prototype.equals)
console.warn("Overriding existing Array.prototype.equals. Possible causes: New API defines the method, there's a framework conflict or you've got double inclusions in your code.");
// attach the .equals method to Array's prototype to call it on any array
Array.prototype.equals = function (array) {
// if the other array is a falsy value, return
if (!array)
return false;
// compare lengths - can save a lot of time
if (this.length != array.length)
return false;
for (var i = 0, l = this.length; i < l; i++) {
// Check if we have nested arrays
if (this[i] instanceof Array && array[i] instanceof Array) {
// recurse into the nested arrays
if (!this[i].equals(array[i]))
return false;
}
else if (this[i] != array[i]) {
// Warning - two different object instances will never be equal: {x:20} != {x:20}
return false;
}
}
return true;
}
// Hide method from for-in loops
Object.defineProperty(Array.prototype, "equals", {enumerable: false});该专家同时提供了比较Object的方法：
Object.prototype.equals = function(object2) {
//For the first loop, we only check for types
for (propName in this) {
//Check for inherited methods and properties - like .equals itself
//https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/hasOwnProperty
//Return false if the return value is different
if (this.hasOwnProperty(propName) != object2.hasOwnProperty(propName)) {
return false;
}
//Check instance type
else if (typeof this[propName] != typeof object2[propName]) {
//Different types => not equal
return false;
}
}
//Now a deeper check using other objects property names
for(propName in object2) {
//We must check instances anyway, there may be a property that only exists in object2
//I wonder, if remembering the checked values from the first loop would be faster or not
if (this.hasOwnProperty(propName) != object2.hasOwnProperty(propName)) {
return false;
}
else if (typeof this[propName] != typeof object2[propName]) {
return false;
}
//If the property is inherited, do not check any more (it must be equa if both objects inherit it)
if(!this.hasOwnProperty(propName))
continue;
//Now the detail check and recursion
//This returns the script back to the array comparing
/**REQUIRES Array.equals**/
if (this[propName] instanceof Array && object2[propName] instanceof Array) {
// recurse into the nested arrays
if (!this[propName].equals(object2[propName]))
return false;
}
else if (this[propName] instanceof Object && object2[propName] instanceof Object) {
// recurse into another objects
//console.log("Recursing to compare ", this[propName],"with",object2[propName], " both named \""+propName+"\"");
if (!this[propName].equals(object2[propName]))
return false;
}
//Normal value comparison for strings and numbers
else if(this[propName] != object2[propName]) {
return false;
}
}
//If everything passed, let's say YES
return true;
} 以上内容为小编整理的JavaScript比较两个数组内容是否相同(推荐)教程，希望能对大家有所帮助。如有任何疑问，欢迎留言，小编将及时回复。在此衷心感谢大家对本站的支持！