5.3.搜索匹配的数组元素

5.3. 搜索匹配的数组元素

问题
我要找出指定值得数组元素
解决办法
用for 语句和break 语句就能找到匹配的元素。另外用ArrayUtilities.findMatchIndex( ), ArrayUtilities.findLastMatchIndex( ), 和ArrayUtilities.findMatchIndices( ) 方法
讨论

用for循环查找第一个匹配的元素后，用break立即返回，这样就实现功能了。
break应该在if语句里进行判断，是否找到匹配元素，找到则执行break推出循环，否则继续查找。
var letters:Array = ["a", "b", "c", "d", "a", "b", "c", "d"];

// 指定要搜索的内容
var match:String = "b";

for (var i:int = 0; i < letters.length; i++) {

// 检测当前元素是否匹配
if (letters[i] == match) {
trace("Element with index " + i +
" found to match " + match);
break;
}
}
也可以找到匹配的最后一个元素，这就需要倒序遍历数组：
var letters:Array = ["a", "b", "c", "d", "a", "b", "c", "d"];

var match:String = "b";
for (var i:int = letters.length - 1; i >= 0; i--) {
if (letters[i] == match) {
trace("Element with index " + i +
" found to match " + match);
break;
}
}
使用自定义类ArrayUtilities 类更简单，它在 ascb.util 包中，首先导入它：
import ascb.util.ArrayUtilities;
ArrayUtilities 类有三个方法来查找匹配的元素findMatchIndex( ), findLastMatchIndex( ), 和 findMatchIndices( )。 findMatchIndex( ) 方法至少需要两个参数：一个指向数组的引用和需要匹配的值，返回第一个匹配的元素下标，如果找不到返回-1：
var letters:Array = ["a", "b", "c", "d"];
trace(ArrayUtilities.findMatchIndex(letters, "b"));
// 显示: 1
trace(ArrayUtilities.findMatchIndex(letters, "r"));
// 显示: -1
也可以指定搜索的起始下标作为第三个参数：
var letters:Array = ["a", "b", "c", "d", "a", "b", "c", "d"];
trace(ArrayUtilities.findMatchIndex(letters, "a", 1));
// 显示: 4
如果第三个参数为true，则返回部分匹配的元素：
var words:Array = ["bicycle", "baseball", "mat", "board"];
trace(ArrayUtilities.findMatchIndex(words, "s", true));
// 显示: 1
如果你想部分匹配又想指定起始搜索下标，可以把起始下标作为第四个参数。
findLastMatchIndex( ) 方法返回最后一个匹配的元素下标
findMatchIndices( ) 方法返回所有匹配的元素下标数组：
var letters:Array = ["a", "b", "c", "d", "a", "b", "c", "d"];
trace(ArrayUtilities.findMatchIndices(letters, "b"));
// 显示: 1,5
也可以设定为部分匹配，指定第三个参数为true：
var words:Array = ["bicycle", "baseball", "mat", "board"];

trace(ArrayUtilities.findMatchIndices(words, "b", true));
// 显示: 0,1,3
ArrayUtilities 方法内部也是用for循环来实现的，现在我们看看代码，下面是findMatchIndex( ) 方法的代码：

public static function findMatchIndex(array:Array, element:Object):int ...{
// Use a variable to determine the index
// from which to start. Use a default value of 0.
var startingIndex:int = 0;

// By default don't allow a partial match.
var partialMatch:Boolean = false;

// If the third parameter is a number,
// assign it to nStartingIndex.
// Otherwise, if the fourth parameter is a number,
// assign it to nStartingIndex instead.
if(typeof arguments[2] == "number") ...{
startingIndex = arguments[2];
}
else if(typeof arguments[3] == "number") ...{
startingIndex = arguments[3];
}

// If the third parameter is a Boolean value,
// assign it to partialMatch.
if(typeof arguments[2] == "boolean") ...{
partialMatch = arguments[2];
}

// Assume no match is found.
var match:Boolean = false;

// Loop through each of the elements of the array
// starting at the specified starting index.
for(var i:int = startingIndex;
i < array.length; i++) ...{

// Check to see if the element either matches
// or partially matches.
if(partialMatch) ...{
match = (array[i].indexOf(element) != -1);
}
else ...{
match = (array[i] == element);
}

// If the element matches, return the index.
if(match) ...{
return i;
}
}

// The following return statement is only reached
// if no match was found. In that case, return -1.
return -1;
}

public static function findMatchIndices(array:Array,
element:Object, partialMatch:Boolean = false):Array ...{
var indices:Array = new Array( );
var index:int = findMatchIndex(array,
element,
partialMatch);
while(index != -1) ...{
indices.push(index);
index = findMatchIndex(array,
element,
partialMatch,
index + 1);
}
return indices;
}