javascript - How to run corresponding function based on variable content?

I wrote several functions funA(x), funB(x), funC(x), funD(x), funE(x), funF(x). Now I have a requirement, based on a certain parameter str , to implement different calculations. For example, when str='abc', x→funA(x)→funB(x)→funC(x)→y can be executed. When str'ace', x→funA(x)→funC( x)→funE(x)→y.

<code>function fun_abc(x)
{
    var a = funA(x);
    var b = funB(a);
    var c = funC(b);

    var y = c;
    
    return y;
}</code>

I know that I can write a switch to make a case based on str and jump to different fun_XXX(), but this is not flexible. My ultimate goal is to have an array with different function names written in order. When calling, input x, run the function corresponding to the first element in the array to the last function, and output the final result y.

Is there any other way to abbreviate it? Or can free combination be achieved, for example, directly executing a function with the same name based on a variable, like funstr='abc', running something like funstr(x) will execute function abc(x)?

js or php related syntax is acceptable.

Reply content:

I wrote several functions funA(x), funB(x), funC(x), funD(x), funE(x), funF(x). Now I have a requirement, based on a certain parameter str , to implement different calculations. For example, when str='abc', x→funA(x)→funB(x)→funC(x)→y can be executed. When str'ace', x→funA(x)→funC( x)→funE(x)→y.

<code>function fun_abc(x)
{
    var a = funA(x);
    var b = funB(a);
    var c = funC(b);

    var y = c;
    
    return y;
}</code>

I know that I can write a switch to make a case based on str and jump to different fun_XXX(), but this is not flexible. My ultimate goal is to have an array with different function names written in order. When calling, input x, run the function corresponding to the first element in the array to the last function, and output the final result y.

Is there any other way to abbreviate it? Or can free combination be achieved, for example, directly executing a function with the same name based on a variable, like funstr='abc', running something like funstr(x) will execute function abc(x)?

js or php related syntax is acceptable.

Let me give you an example, eval is too rude. . . Big brother, come and see me

<code>function run(str, param) {
  let handle = { a: a, b: b, c: c, d: d };
  return str.split('').reduce((res, name) => handle[name](res), param);

  function a(x) {
    return x + '1';
  }
  function b(x) {
    return x + '2';
  }
  function c(x) {
    return x + '3';
  }
  function d(x) {
    return x + '4';
  }
}

run('acb',0); // "0132"</code>

For example, similar ideas can be freely used

Improved on the basis of @ fish who don’t like tomatoes

• Every time you call the run function, four functions and a map must be generated, which is relatively expensive. You can carry it outside run.

• Use reduce instead of forEach

<code>const funcTable = { a, b, c, d }

function run(str, initialVal) {
  return str.split('').reduce((result, funcName) => funcTable[funcName](result), initialVal)
}

// 定义function a， function b...</code>

The simplest, eval
Troublesome {'abc': fabc}

The idea is very simple, I will post a sample code for both php and node

php version

<code>function funstr($str,$param){
    $len = strlen($str);
    for($i=0;$i<$len;$i++){
        $fun = 'fun'.strtoupper(substr($str,$i,1));
        if(function_exists($fun)){
            $param = $fun($param);
        }
    }
    return $param;
}

function funA($x) {
    return $x+1;
}

function funB($x) {
    return $x+2;
}

echo funstr('ab',0); // 输出3</code>

node version

<code>function funstr(str,x) {
  var len = str.length;
  for(var i=0; i<len; i++){
    var fun = 'fun'+ str.charAt(i).toUpperCase();
    x = eval(fun+'('+x+')');
  }
  return x;
}

function funA(x){
  return x+1;
}

function funB(x){
  return x+2;
}

console.log(funstr('ab',0));//输出3</code>

Put all the defined functions in an object, set the return value and call it;
var ab={

<code>    a:function(x){console.log(x);return 1},
    b:function(x){console.log(x);return 2},
    c:function(x){console.log(x);return 3},
    d:function(x){console.log(x);return 4},
}
function run(str,x){//str是定义的顺序，如acb；x是你要传的参数
    var b=x;
    var aa=str.split("")
    aa.forEach(function(x){
        ab[x](b);
        b=ab[x](b);
    })
    return b
}</code>