JavaScript中符号“+”的含义？

Question

+是什么意思？它

实施例的使用：

var svg = d3.select("svg"), 
    width = +svg.attr("width"), 
    height = +svg.attr("height"); 

Answer 1

务实角度来说，它的JavaScript简写的值转换为Number。从技术上讲，它是unary plus operator，与unary negation operator互补。

let number = "1" 
 

 
console.log(typeof number) 
 

 
console.log(typeof +number) 
 
console.log(+number) 
 

 
console.log(typeof -number) 
 
console.log(-number) 
 

 
console.log(typeof +true) 
 
console.log(+true)