使用函数和参数从关联数组中获取最大值或最小值
[英]Get max or min value from associative array with function and parameters
问题描述
Here is the code as far as I got it right now: 
这是我目前所获得的代码：
<!DOCTYPE html>
<html>
<body>
<button onclick="scanarray('a', 'max')">Test with a, max</button>
<button onclick="scanarray('b', 'min')">Test with b, min</button>
<p id="demo">test</p>
<script>
var array = [{"a":1},{"b":3},{"a":6},{"b":10}];
var max = null;
var min = null;
var value = null;
function scanarray(scanval, searchterm) {
if (array.length < 1) {
return -1;
}
if(searchterm == "max"){
max = Math.max.apply(Math,array.map(function(e){return e.scanvalue;}))
}else if (searchterm == "min"){
min = Math.min.apply(Math,array.map(function(e){return e.scanval;}))
}else
{document.getElementById("demo").innerHTML = "Only max and min available";}
if(searchterm == "max"){
document.getElementById("demo").innerHTML = "Search: " + scanval +" "+ "Value: " + max;
}
if(searchterm == "min"){
document.getElementById("demo").innerHTML = "Search: " + scanval +" "+ "Value: " + min;
}
}
</script>
</body>
</html>
The above should give me a and 6 or b and 3 as results. 以上应该给我a和6或b和3作为结果。 However I get NaN as result for the value part. 但是我得到NaN作为价值部分的结果。 When using "return ea" in the Math section and only having a as keys it works. 在“数学”部分中使用“ return ea”并且仅将a作为键时，它可以工作。
I want to be able to determin the max or min value of a key I enter as parameter to the function. 我希望能够确定作为函数参数输入的键的最大值或最小值。
Hope you can help me here. 希望你能在这里帮助我。
Thanks in advance. 提前致谢。
TheVagabond 流浪者
2 个解决方案
解决方案1
1 已采纳 2016-08-01 13:25:37
There are some naming mess in your code. 您的代码中有些命名混乱。 For example scanvalue is name of your function but you are trying to reach it as a parameter of e( e.scanvalue ). 例如， scanvalue是函数的名称，但是您尝试将其作为e（ e.scanvalue ）的参数来e.scanvalue 。 I should be scanval . 我应该是scanval 。 But still there are some problems. 但是仍然存在一些问题。 You can't reach property "a" or "b" of e if e.scanval . 如果e.scanval则无法访问e的属性“ a”或“ b”。 You're trying to reach variable of variable . 您正在尝试达到variable的变量 。
Then, you should use e[scanval] . 然后，您应该使用e[scanval] 。 It returns you to value of "a" or "b". 它使您返回到“ a”或“ b”的值。 But if object doesn't have one of them? 但是，如果对象没有其中之一？ Then you should add "|| 0" to get correct value. 然后，您应该添加“ || 0”以获得正确的值。 (Instead of NaN or undefined) It means that; （而不是NaN或未定义） 是指； use e[scanval] if its valid, if not use 0. 如果有效，请使用e [scanval]，否则请不要使用0。
Use this; 用这个;
return e[scanval] || 0;
If your boundaries include some negative values, use something like -9999 or -Infinity.
解决方案2
0 2016-08-01 13:33:05
You are getting Nan because e.scanvalue returns undefined in your case. 您得到Nan的原因是e.scanvalue在您的情况下返回undefined。
Try using custom function. 尝试使用自定义功能。
function getValue(arr){
var res = [];
for(var j = 0; j < arr.length; j++)
{
for(var anItem in arr[j])
{
res.push(arr[j][anItem]);
}
}
return res;
}
and call this function like 并像这样调用此函数
max = Math.max.apply(Math,getValue(array))
and 和
min = Math.min.apply(Math,getValue(array))
accordingly. 相应地。 Hope this helps!!!! 希望这可以帮助！！！！
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