D3.js formatPrefix()函数

D3.js 中的formatPrefix()函数用于将值转换为给定数字的适当 SI 前缀的单位，例如 pico、femto、milli 等。

句法：

d3.formatPrefix(specifier, value);

参数：它采用上面给出和下面描述的两个参数。

• 说明符：它是说明格式样式的说明符。
• 值：它是在定点符号格式化之前指定的数值参考值。

返回值：此方法返回一个函数。

下面给出了几个 formatPrefix()函数的例子。

示例 1：

  
  
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    // It is the Floating point up to two decimals
    // value is 1e-1
    console.log(d3.formatPrefix(".4s", 1e-1)(58))
    // It sets the SI-Prefix with two significant digits
    // value is 1e-2
    console.log(d3.formatPrefix(".4s", 1e-2)(42000))
    // Currency sign i.e $
    // value is 1e-3
    console.log(d3.formatPrefix("$, ", 1e-3)(4200))
    // Filled with dots and centered in between them
    // value is 1e-4
    console.log(d3.formatPrefix("^, ", 1e-14)(42.444))
    // Localised fixed-point currency
    // value is 1e-5
    console.log(d3.formatPrefix("($.2f", 1e-5)(42.444))
    // value is 1e-8
    console.log(d3.formatPrefix("#", 1e-18)(2))
    // value is 1e-9
    console.log(d3.formatPrefix("#s", 1e-9)(42))
    // Number is grouped thousand with two significant digits
    // value is 1e-12
    console.log(d3.formatPrefix(", .2r", 1e-12)(421))
 

输出：

示例 2：

  
  
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    // It is the Floating point up to two decimals
    // value is 1e-24
    console.log(
"y- yocto: ", d3.formatPrefix(".4s", 1e-24)(58))
    // It sets the SI-Prefix with two significant digits
    // value is 1e-21
    console.log(
"z-zepto: ", d3.formatPrefix(".4s", 1e-21)(42000))
    // Currency sign i.e $
    // value is 1e-15
    console.log(
"f-femto: ", d3.formatPrefix("$, ", 1e-15)(4200))
    // value is 1e-6
    console.log(
"micro: ", d3.formatPrefix("^, ", 1e-6)(42.444))
    // value is 1e+3
    console.log(
"k-kilo: ", d3.formatPrefix("($.2f", 1e+3)(42.444))
    // value is 1e-9
    console.log(
"n-nano: ", d3.formatPrefix(".4s", 1e-9)(4))
    // value is 1e+18
    console.log(
"E-exa: ", d3.formatPrefix(".4s", 1e+18)(424))
    // value is 1e+24
    console.log(
"Y-yotta: ", d3.formatPrefix(".2f", 1e+24)(0))
 

输出：