如何在打字稿Angular 4中将字符串转换为布尔值

Question

I know am not the first to ask this and as I mentioned in my title ,I am trying to convert string value boolean .

I have previously put some values into local storage,Now I want to get all the values and assign all to the some boolean variables .

app.component.ts

localStorage.setItem('CheckOutPageReload', this.btnLoginNumOne + ',' + this.btnLoginEdit);

here this.btnLoginNumOne and this.btnLoginEdit are string values ("true,false") .

mirror.component.ts

if (localStorage.getItem('CheckOutPageReload')) {
      let stringToSplit = localStorage.getItem('CheckOutPageReload');
      this.pageLoadParams = stringToSplit.split(',');

      this.btnLoginNumOne = this.pageLoadParams[0]; //here I got the error as boolean value is not assignable to string
      this.btnLoginEdit = this.pageLoadParams[1]; //here I got the error as boolean value is not assignable to string
}

in this component this.btnLoginNumOn e and this.btnLoginEdi t are Boolean values;

I tried the solutions in stackoverflow but nothing is worked.

Can anyone help me to fix this .

Answer 1

Method 1 :

var stringValue = "true";
var boolValue = (/true/i).test(stringValue) //returns true

Method 2 :

var stringValue = "true";
var boolValue = (stringValue =="true");   //returns true

Method 3 :

var stringValue = "true";
var boolValue = JSON.parse(stringValue);   //returns true

Method 4 :

var stringValue = "true";
var boolValue = stringValue.toLowerCase() == 'true'; //returns true

Method 5 :

var stringValue = "true";
var boolValue = getBoolean(stringValue); //returns true
function getBoolean(value){
   switch(value){
        case true:
        case "true":
        case 1:
        case "1":
        case "on":
        case "yes":
            return true;
        default: 
            return false;
    }
}

source:http://codippa.com/how-to-convert-string-to-boolean-javascript/

Answer 2

I have been trying different values with JSON.parse(value) and it seems to do the work:

// true
Boolean(JSON.parse("true"));
Boolean(JSON.parse("1"));
Boolean(JSON.parse(1));
Boolean(JSON.parse(true));

// false
Boolean(JSON.parse("0")); 
Boolean(JSON.parse(0));
Boolean(JSON.parse("false"));
Boolean(JSON.parse(false));

Answer 3

In your scenario, converting a string to a boolean can be done via something like someString === 'true' (as was already answered).

However, let me try to address your main issue: dealing with the local storage.

The local storage only supports strings as values; a good way of using it would thus be to always serialise your data as a string before storing it in the storage, and reversing the process when fetching it.

A possibly decent format for serialising your data in is JSON, since it is very easy to deal with in JavaScript.

The following functions could thus be used to interact with local storage, provided that your data can be serialised into JSON.

function setItemInStorage(key, item) {
  localStorage.setItem(key, JSON.stringify(item));
}

function getItemFromStorage(key) {
  return JSON.parse(localStorage.getItem(key));
}

Your example could then be rewritten as:

setItemInStorage('CheckOutPageReload', [this.btnLoginNumOne, this.btnLoginEdit]);

And:

const pageLoadParams = getItemFromStorage('CheckOutPageReload');
if (pageLoadParams) {
  this.btnLoginNumOne = pageLoadParams[0];
  this.btnLoginEdit = pageLoadParams[1];
}

Answer 4

Define extension: String+Extension.ts

interface String {
  toBoolean(): boolean
}

String.prototype.toBoolean = function (): boolean {
  switch (this) {
    case 'true':
    case '1':
    case 'on':
    case 'yes':
      return true
    default:
      return false
  }
}

And import in any file where you want to use it '@/path/to/String+Extension'

Answer 5

This function will convert your string to boolean

export const stringToBoolean = (str: string | null | undefined) => {
    if (!str) {
        return false
    }
    if (typeof str === "string") {
        return !["0", "false", "no", "n", "null", "undefined", "nil"].includes(str.toLowerCase().trim())
    }
    return Boolean(str)
}

Answer 6

I think this is most accurate:

function parseBoolean(value?: string | number | boolean | null) {
    value = value?.toString().toLowerCase();
    return value === 'true' || value === '1';
}

Answer 7

just use << !! >> operator:

const Text1 = ""
const Text2 = "there is a text"

console.log(!!Text1) // false
console.log(!!Text2) // true

Answer 8

You can use that:

let s: string = "true";
let b: boolean = Boolean(s);

Answer 9

You could also try using the bang bang operator if you know its a valid boolean value in the string. for eg

let trueAsString = 'true';

let convertedStringToBool = !!trueAsString;

Answer 10

Boolean("true") 也可以完成这项工作