substr()

描述 (Description)

此方法用于返回字符串的必需子字符串。 它接受一个整数值，表示子字符串的起始值和字符串的长度，并返回所需的子字符串。 如果起始值为负，则substr()方法将其用作字符串末尾的字符索引。

语法 (Syntax)

下面给出了JavaScript的substr()方法的语法。 我们可以在CoffeeScript代码中使用相同的方法。

string.substr(start[, length])

例子 (Example)

以下示例演示了CoffeeScript代码中JavaScript的substr()方法的用法。 将此代码保存在名为string_substr.coffee的文件中

str = "Apples are round, and apples are juicy.";
console.log "The sub string having start and length as (1,2) is : " + str.substr 1,2
console.log "The sub string having start and length as (-2,2) is : " + str.substr -2,2
console.log "The sub string having start and length as (1) is : " + str.substr 1
console.log "The sub string having start and length as (-20, 2) is : " + str.substr -20,2
console.log "The sub string having start and length as (20, 2) is : " + str.substr 20,2;

打开command prompt并编译.coffee文件，如下所示。

c:\> coffee -c coffee string_substr.coffee

在编译时，它为您提供以下JavaScript。

// Generated by CoffeeScript 1.10.0
(function() {
  var str;
  str = "Apples are round, and apples are juicy.";
  console.log("The sub string having start and length as (1,2) is : " + str.substr(1, 2));
  console.log("The sub string having start and length as (-2,2) is : " + str.substr(-2, 2));
  console.log("The sub string having start and length as (1) is : " + str.substr(1));
  console.log("The sub string having start and length as (-20, 2) is : " + str.substr(-20, 2));
  console.log("The sub string having start and length as (20, 2) is : " + str.substr(20, 2));
}).call(this);

现在，再次打开command prompt并运行CoffeeScript文件，如下所示。

c:\> coffee string_substr.coffee 

执行时，CoffeeScript文件生成以下输出。

The sub string having start and length as (1,2) is : pp
The sub string having start and length as (-2,2) is : y.
The sub string having start and length as (1) is : pples are round, and apples are juicy.
The sub string having start and length as (-20, 2) is : nd
The sub string having start and length as (20, 2) is : d