与表达式连接的空格有时会被删除

Question

JSFiddle包含：

import numpy as np
import scipy.stats as stats
from scipy.stats import poisson, norm

mu = 4.68
cs = 100
co = 300
G = poisson(mu)
p = G.pmf(np.arange(3*mu))

def Z(Q):
    ES = sum(i*p[i] for i in range(len(p)))
    return co*max((Q-ES), 0) + cs*max((ES-Q), 0)

Qstar = np.ceil(poisson.ppf(co/(cs+co), mu))
print(Qstar)

Qstar = int(np.float64(Qstar).item())


from scipy.integrate import quad
import pylab as pl

x = []

y = []

for Q in range(0, Qstar):
    x.append(Q)
    y.append(Z(Q))

pl.plot(x, y)

pl.show()

为什么var d = " " + true ? "am" : "pm"; var e = " " + "am"; alert("|" + d + "|"); alert("|" + e + "|"); 不包含前导空格？

Answer 1

你想要var d = " " + (true ? "am" : "pm")

Answer 2

Check the edit here.

javascript操作顺序是在三元运算符之前计算" " + true。

Answer 3

“”+ true计算为布尔值..你需要

var d = " " + (true ? "am" : "pm");

Answer 4

你正试图这样做 var d = (" " + true) ? "am" : "pm" 在您的情况下，条件为" " + true。 正确的条件是var d = (true ? "am" : "pm")

var d = " " + true ? "am" : "pm";   //output    |am|
var d = (" " + true) ? "am" : "pm";   //output  |am|
var d = " " + (true ? "am" : "pm");   //output  | am|