SOURCE

function calc(a, option, b) {
  let res;
  let formula;
  if (option == '+') {
    res = a.value + b.value;
    formula=a.formula+'+'+b.formula;
  }
  else if (option == '-') {
    res = a.value - b.value;
    formula=a.formula+'-'+b.formula;
  }
  else if (option == '*') {
    res = a.value * b.value;
    formula=a.formula+'*'+b.formula;
  }
  else if (option == '/') {
    res =a.value / b.value;
    formula=a.formula+'/'+b.formula;
  }
  else if(option == '.'){
    res=Number([a.value , b.value].join(""));
    formula=a.formula+'.'+b.formula;
  }
  if (res < 0) {
    res= NaN;
  }
  else if (res % 1 !== 0) {
    res=NaN
  }
  return  {
    value:res,
    formula:'('+formula+')',
  };;
};
let cache = {};
function calcSum(nums, options, target) {
  let cha=nums.length-1-options.length;
  if(cha){
    options.push(...'.'.repeat(cha))
  }
  cache={}
  options.sort()
  for(let i of nums){
    cache[i]={
      value:i,
      formula:i,
    }
  }
  calcLoop(nums, options, target)
};
function calcLoop(nums, options, target){
  if (nums.length === 1 &&options.length==0&& cache[nums[0]].value == target) {
    console.log(nums[0]);
    return;
  }
  nums.sort()
  let key=[...nums].join()+'|'+options.join();
  if(cache[key]){
    return
  }
  cache[key]=true
  for (let i of '*+-/.') {
    let index = options.indexOf(i);
    if (index >= 0) {
      let newOptions = [...options];
      newOptions.splice(index, 1);
      let len=nums.length
      for (let j=0;j<len-1;j++) {
        let newNums=[...nums];
        newNums.splice(nums.indexOf(nums[j]), 1);
        for(let k=j+1;k<len;k++){
          let newNums2=[...newNums];
          newNums2.splice(newNums2.indexOf(nums[k]), 1);
          let newNum = calc(cache[nums[j]], i, cache[nums[k]])
          if (isNaN(newNum.value)) {
          }
          else{
            cache[newNum.formula]=newNum;
            let t=[newNum.formula,...newNums2];
            calcLoop(t, newOptions, target);
          }
          if(i!='+'&&i!='*'){
            let newNum = calc(cache[nums[k]], i, cache[nums[j]]);
            if (isNaN(newNum.value)) {
            }
            else{
              cache[newNum.formula]=newNum;
              let t=[newNum.formula,...newNums2];
              calcLoop(t, newOptions, target);
            }
          }
        }
      }
    }
  }
}