javascript - 我的 if 语句和 else if 语句没有被执行，但没有错误

Question

所以我正在写一个计算器，我在等号上苦苦挣扎，我正在尝试做一些简单的床（没有括号也没有指数），但我的代码一直返回 0，就好像 if 语句完全被跳过了

我不知道是什么原因造成的，因为我没有收到任何错误

function equal(){
        let exp = document.form.textview.value;
        let expArray = exp.split(/\b/);
        console.log(expArray);   //<-if something doesn't work check this
        let total = 0;
        var lastOperator = "+";
        var lastDig = 0;
        for(let i = 0 ; i < expArray.length; i++){
          var dig = expArray[i].trim(); //value of "i", the item currently in the loop
          if(isNaN(dig) == true){
             console.log("string")
           }
          else if(isNaN(dig) == false){
            console.log('not string');
              if (dig == "/"){ //this whole section gets skipped :(
                var a = i + 1;
                var p = i - 1;
                var aDig = parseFloat(expArray[a].trim); //value after "i"
                var bDig = parseFloat(expArray[p].trim); // value before  "i"
                var sDig = aDig / bDig;
                total = expArray.splice(bDig, 3, sDig);
              }

              else if ( dig == "*"){
                var a = i + 1;
                var p = i - 1;
                var aDig = parseFloat(expArray[a].trim); //value after "i"
                var bDig = parseFloat(expArray[p].trim) // value before  "i"
                var sDig = aDig * bDig;
                total = expArray.splice(bDig, 3, sDig);
              }
              else if ( dig == "+"){
                var a = i + 1;
                var p = i - 1;
                var aDig = parseFloat(expArray[a].trim); //value after "i"
                var bDig = parseFloat(expArray[p].trim)// value before  "i"
                var sDig = aDig + bDig;
                total = expArray.splice(bDig, 3, sDig);
                console.log(expArray.splice(bDig, 3, sDig));
              }
              else if( dig == "-"){
                var a = i + 1;
                var p = i - 1;
                var aDig = parseFloat(expArray[a].trim); //value after "i"
                var bDig = parseFloat(expArray[p].trim) // value before  "i"
                var sDig = aDig - bDig;
                total = expArray.splice(bDig, 3, sDig);
            }
          }

            }
            document.form.textview.value = total;

        } ```

标签： javascriptfor-loopif-statementcalculatorcalculation

Answer 1

我不确定您到底想在这里做什么。isNan(numberContent) 将返回 false & isNan(stringContent) 将返回 true。你用错了。第一个 if 应该是isNaN(dig) == false& 2nd isNaN(dig) == true。

        let exp = "1/1*3";
        let expArray = exp.split(/\b/);
        console.log(expArray);   //if something doesn't work check this
        var previousValue= parseFloat(expArray[0].trim().toString());
        for(let i = 1 ; i < expArray.length; i++){
        var dig = expArray[i].trim(); //value of "i", the item currently in the loop
          if(isNaN(dig) == false){
             console.log("string")
           }
          else if(isNaN(dig) == true){
            console.log("not string");
            
              var a = i + 1;
              var aDig = previousValue
              var bDig =  parseFloat(expArray[a].trim().toString()); //value after "i"; // value before  "i"
              if (dig == "/"){ //this whole section gets skipped :(
                var sDig = aDig / bDig;
              }

              else if ( dig == "*"){
                var sDig = aDig * bDig;
              }
              else if ( dig == "+"){
                var sDig = aDig + bDig;
                
              }
              else if( dig == "-"){
                var sDig = aDig - bDig;
            }
            previousValue = sDig;
            i++
          }

            }
       alert(previousValue);

        ```