本文介紹了JavaScript 字符串和數字轉換的處理方法，對大家解決問題具有一定的參考價值，需要的朋友們下面隨著小編來一起學習吧！
問題描述
如何在 JavaScript 中執行以下操作?
How can I do the following in JavaScript?
將1"、2"、3"連接成123"
Concatenate "1", "2", "3" into "123"
將123"轉換為123
Convert "123" into 123
加 123 + 100 = 223
Add 123 + 100 = 223
將223轉換為223"
Covert 223 into "223"
推薦答案
你想熟悉 parseInt() 和 toString().
在您的工具包中有用的是查看變量以找出它是什么類型—typeof:
And useful in your toolkit will be to look at a variable to find out what type it is—typeof:
<script type="text/javascript">
/**
* print out the value and the type of the variable passed in
*/
function printWithType(val) {
document.write('<pre>');
document.write(val);
document.write(' ');
document.writeln(typeof val);
document.write('</pre>');
}
var a = "1", b = "2", c = "3", result;
// Step (1) Concatenate "1", "2", "3" into "123"
// - concatenation operator is just "+", as long
// as all the items are strings, this works
result = a + b + c;
printWithType(result); //123 string
// - If they were not strings you could do
result = a.toString() + b.toString() + c.toString();
printWithType(result); // 123 string
// Step (2) Convert "123" into 123
result = parseInt(result,10);
printWithType(result); // 123 number
// Step (3) Add 123 + 100 = 223
result = result + 100;
printWithType(result); // 223 number
// Step (4) Convert 223 into "223"
result = result.toString(); //
printWithType(result); // 223 string
// If you concatenate a number with a
// blank string, you get a string
result = result + "";
printWithType(result); //223 string
</script>
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