[英]how can i add a value from an array to a value from an another one in javascript?
So, I have two arrays: grade[] and grade2[] that contains elements I give from windows.prompt . 因此,我有两个数组:grade []和grade2 [],它们包含我从windows.prompt提供的元素。 I want to add a value from grade with a value from grade2 so i can calculate "media".
我想将年级的值与年级2的值相加,以便可以计算“媒体”。 But the code that i wrote just concats those two values, doesn't add them actually.
但是我编写的代码只是合并了这两个值,实际上并没有将它们相加。 I am a beginner and I hope you can help me.
我是一个初学者,希望您能帮助我。 Thank you!
谢谢!
function display_student()
{
var n=window.prompt("Number of students: "+"");
var name= new Array(n);
var grade=new Array(n);
var grade2=new Array(n);
var y=0;
for (y=0; y<n; y++)
{
name[y]=window.prompt("Student name:","");
grade[y]=window.prompt("Grade 1: ","5");
grade2[y]=window.prompt("Grade 2: ","5")
document.write("</br>"+"Student name: "+name[y]+"</br>"+"Grade 1: "+grade[y]+" </br>"+"Grade 2: "+grade2[y]+"</br>");
var media=(grade[y]+grade2[y])/2;
document.write("Media: "+media+"</br>");
if(media<5)
document.write("Failed");
else
document.write("Promoted");
}
}
添加之前,请使用parseInt
函数。
var media=(parseInt(grade[y]) + parseInt(grade2[y]))/2;
Because they are strings and no numbers. 因为它们是字符串,没有数字。
Take a look at parseInt(string, radix)
看看
parseInt(string, radix)
The values in the array are of type String
( as returned by the window.prompt function ) you need to convert them to numbers to add them together : 数组中的值是
String
类型( 由window.prompt函数返回 ),您需要将它们转换为数字以将它们加在一起:
function display_student() {
var n = window.prompt("Number of students: " + "");
var name = new Array(n);
var grade = new Array(n);
var grade2 = new Array(n);
var y = 0;
for (y = 0; y < n; y++) {
name[y] = window.prompt("Student name:", "");
grade[y] = window.prompt("Grade 1: ", "5");
grade2[y] = window.prompt("Grade 2: ", "5"); // added semi-colon here too
document.write("</br>" + "Student name: " + name[y] + "</br>" + "Grade 1: " + grade[y] + " </br>" + "Grade 2: " + grade2[y] + "</br>");
var media = (parseFloat(grade[y]) + parseFloat(grade2[y])) / 2;
document.write("Media: " + media + "</br>");
if (media < 5) {
document.write("Failed");
} else {
document.write("Promoted");
}
}
}
Working example : http://jsfiddle.net/z5cUw/ 工作示例: http : //jsfiddle.net/z5cUw/
Use: 采用:
var media=(parseInt(grade[y], 10)+parseInt(grade2[y], 10))/2;
Assuming your grades are integers. 假设您的成绩是整数。 Otherwise, use
parseFloat
(in that case, you won't need the second parameter). 否则,请使用
parseFloat
(在这种情况下,您将不需要第二个参数)。
使用parseFloat:
var media=(parseFloat(grade[y])+parseFloat(grade2[y]))/2;
This is an indirect answer because this is tagged homework. 这是一个间接答案,因为这被标记为作业。
Because window.prompt returns a string by default, you need to convert this string to a number. 由于window.prompt默认返回一个字符串,因此您需要将此字符串转换为数字。 There are several methods to do this.
有几种方法可以做到这一点。
parseInt()
as several people have suggested. parseInt()
。 Returns an integer value. parseFloat()
as suggested. parseFloat()
。 window.prompt("Grade 1: ","5")/1;
window.prompt("Grade 1: ","5")/1;
or during the media calculation: var media = (grade[y]/1 + grade2[y]/1) / 2;
var media = (grade[y]/1 + grade2[y]/1) / 2;
Number(window.prompt("Grade 1: ", "5"));
Number(window.prompt("Grade 1: ", "5"));
It is up to you to determine which is the appropriate method for your needs. 由您决定哪种方法适合您的需求。 What if the value entered is NOT a number?
如果输入的值不是数字怎么办? Study each of these methods to determine which best suites your needs.
研究每种方法,以确定最适合您的需求。
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