Question

这里是我努力奋斗的代码。我想将两个输入连在一起，并将结果保存为整数（JS中的数字＆＃39; s）。

var secsVal = -1;
function valueAssign(i) {

    if (secsVal == -1){

        document.getElementById("countdown").value = i;
        document.getElementById("countdown").innerHTML = (i);

        secsVal = i;
    }
    else {      
        secsVal = "" + secsVal + i;//concatenating first value of i to the second.
        secsVal = secsVal.map(Number);//trying to convert back to num, but I think map() needs to see an array, which I don't think I got here.

        document.getElementById("countdown").value = secsVal;
        document.getElementById("countdown").innerHTML = (secsVal);//I want to replace the first displayed digit here, with the new (concatenated) number.
    }
}

Answer 1

试试这个

secsVal = +("" + secsVal + i);

Answer 2

在输入标记中使用数字作为值是没有意义的。类型总是一个字符串。

要转换为数字，请使用Number或一元+

secsVal = Number(secsVal);

或

secsVal = +secsVal;

Answer 3

secsVal = Number('' + secsVal + i)   // explicit cast to number
secsVal = +('' + secsVal + i)        // implicit cast to number
secsVal = parseInt('' + secsVal + i) // explicit cast to integer
secsVal = ~~('' + secsVal + i)       // implicit cast to integer

Answer 4

只需使用+secsVal

即可

＆＃13;

var secsVal = -1;
function valueAssign(i) {

    if (secsVal == -1){

        document.getElementById("countdown").value = i;
        document.getElementById("countdown").innerHTML = (i);

        secsVal = i;
    }
    else {      
        secsVal = "" + secsVal + i;
        console.log(typeof secsVal);//secsVal is a string
        
        secsVal = +secsVal;
        console.log(typeof secsVal); //secsVal is now a number

        document.getElementById("countdown").value = secsVal;
    }
}

＆＃13;

<input type="number" id="countdown"/>
<button onclick="valueAssign(5)">Click</button>

＆＃13;

Answer 5

如何解析String？

“parseInt（）函数解析一个字符串并返回一个整数。” http://www.w3schools.com/jsref/jsref_parseint.asp

JavaScript - 连接两个数字并将结果视为数字

5 个答案: