JavaScript中符號「+」的含義？

Question

+是什麼意思？它

實施例的使用：

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

Answer 1

務實角度來說，它的JavaScript簡寫的值轉換爲Number。從技術上講，它是unary plus operator，與unary negation operator互補。

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)