为什么我的 else if 语句在这种情况下不起作用？

Question

 class GpaCalc{
    constructor(firstName,math,phy,chem){
        this.firstName = firstName;
        this.math = math;
        this.phy = phy;
        this.chem =chem;
    }

    result(){
        let totalNum = this.math + this.phy + this.chem;
        let percentage = (totalNum * 100) / 300;
        if( this.firstName === ``){
            console.log("Please Enter username.")

         //Problem is in this line below
        } else if(this.math > 40 || this.phy < 40 || this.chem < 40){
            console.log("You have Failed!")

        } else if (percentage >= 80){
            console.log(`${this.firstName}, You got A+`)
        } else if (percentage >= 70){
            console.log(`${this.firstName}, You got A`)
        } else if (percentage >= 65){
            console.log(`${this.firstName}, You got A-`)
        } else if (percentage >= 60){
            console.log(`${this.firstName}, You got B`)
        } else if (percentage >= 50){
            console.log(`${this.firstName}, You got C`)
        } else if (percentage >= 40){
            console.log(`${this.firstName}, You got D`)
        } else {
            console.log(`${this.firstName}, You have Failed!`)
        }
    }
}

    const student1 = new GpaCalc(`Zakaria`,50,65,38)
    student1.result() 

I am making a GPA calculator. Where the programme will take out percentage from 3 added subjects. if any students get less than 40% in average, it will show console.log( ${this.firstName}, You have Failed! ) and also if anyone gets less than 40 in a particular sub, it will show You have Failed as from 1st else if line. But after adding that else if (in first else if line) the result is showing `You have failed from first else if, though my Student1 gets above 40

Answer 1

First of all your if else statement should be more clear. Also some mistakes in the if statements this.math > 40 || this.phy < 40 || this.chem < 40. You have this.math > 40 .... and the other bellow... Thats why its not working....

My opinion

 class GpaCalc { constructor(firstName, math, phy, chem) { this.firstName = firstName; this.math = math; this.phy = phy; this.chem = chem; } result() { let totalNum = this.math + this.phy + this.chem; let percentage = (totalNum * 100) / 300; if (this.firstName === ``) { console.log("Please Enter username.") //Problem is in this line below } else { if (this.math < 40 || this.phy < 40 || this.chem < 40) { console.log("You have Failed.") } else if (percentage >= 80) { console.log(`${this,firstName}. You got A+`) } else if (percentage >= 70) { console.log(`${this,firstName}. You got A`) } else if (percentage >= 65) { console.log(`${this,firstName}. You got A-`) } else if (percentage >= 60) { console.log(`${this,firstName}. You got B`) } else if (percentage >= 50) { console.log(`${this,firstName}. You got C`) } else if (percentage >= 40) { console.log(`${this,firstName}. You got D`) } else { console.log(`${this,firstName}, You have Failed,`) } } } } var student1 = new GpaCalc(`Zakaria`, 50. 65, 42) student1.result()

Answer 2

Your logic in the this.math statement of the conditional seems to be mixed up.

It should be this.math < 40 , not this.math > 40 .

Sometimes a quick review of your code will suffice, instead of asking it on a forum that typically doesn't take kindly to extremely easily spotted mistakes.

In this case, you seem to have accidentally mixed the greater-than operator ( > ) with the less-than operator ( < ).

I would recommend in the future that you look over your code when something like this happens.

If your code has a lot of logic, usually it's something that has to do with the logic, not the language or language implementations.

If you're really stuck, then feel free to ask us a question, we'll do the best we can!

I would just recommend you look over your code a bit more before asking a question (I learned the hard way, and believe me - I don't want to do it again) and you will be fine:)

Answer 3

It's going to fail not just because of this.math > 40 should be <40, but also because your chem score is 38, and you entered: "|| this.chem < 40".

Answer 4

According to my understanding of your problem, this could be a possible solution.

 class GpaCalc{ constructor(firstName,math,phy,chem){ this.firstName = firstName; this.math = math; this.phy = phy; this.chem =chem; } result(){ debugger let totalNum = this.math + this.phy + this.chem; let percentage = (totalNum * 100) / 300; if( this.firstName === ``){ alert("Please Enter username.") } else { if (percentage < 40) { alert(`${this.firstName}, You have Failed.`) }else { if ( this.math < 40 || this.phy < 40 || this.chem< 40) { alert("You have Failed,") }else{ if (percentage >= 80){ alert(`${this.firstName}, You got A+`) } else if (percentage >= 70){ alert(`${this.firstName}, You got A`) } else if (percentage >= 65){ alert(`${this.firstName}, You got A-`) } else if (percentage >= 60){ alert(`${this.firstName}, You got B`) } else if (percentage >= 50){ alert(`${this.firstName}, You got C`) } else if (percentage >= 40){ alert(`${this,firstName}, You got D`) } } } } }} const student1 = new GpaCalc(`Zakaria`,50,65,38) const student2 = new GpaCalc(`Zakaria`,38,38,38) const student3 = new GpaCalc(`Zakaria`,60.60;60) student1.result(); student2.result(); student3.result();