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1
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exports.fetch = isFunction(global.fetch) && isFunction(global.ReadableStream)
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2
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3
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exports.writableStream = isFunction(global.WritableStream)
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4
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5
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exports.abortController = isFunction(global.AbortController)
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6
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7
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exports.blobConstructor = false
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8
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try {
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9
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new Blob([new ArrayBuffer(1)])
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10
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exports.blobConstructor = true
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11
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} catch (e) {}
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12
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13
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// The xhr request to example.com may violate some restrictive CSP configurations,
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14
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// so if we're running in a browser that supports `fetch`, avoid calling getXHR()
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15
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// and assume support for certain features below.
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16
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var xhr
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17
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function getXHR () {
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18
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// Cache the xhr value
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19
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if (xhr !== undefined) return xhr
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20
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21
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if (global.XMLHttpRequest) {
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22
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xhr = new global.XMLHttpRequest()
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23
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// If XDomainRequest is available (ie only, where xhr might not work
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24
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// cross domain), use the page location. Otherwise use example.com
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25
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// Note: this doesn't actually make an http request.
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26
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try {
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27
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xhr.open('GET', global.XDomainRequest ? '/' : 'https://example.com')
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28
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} catch(e) {
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29
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xhr = null
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30
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}
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31
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} else {
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32
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// Service workers don't have XHR
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33
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xhr = null
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34
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}
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35
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return xhr
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36
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}
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37
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38
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function checkTypeSupport (type) {
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39
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var xhr = getXHR()
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40
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if (!xhr) return false
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41
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try {
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42
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xhr.responseType = type
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43
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return xhr.responseType === type
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44
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} catch (e) {}
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45
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return false
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46
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}
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47
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48
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// For some strange reason, Safari 7.0 reports typeof global.ArrayBuffer === 'object'.
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49
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// Safari 7.1 appears to have fixed this bug.
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50
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var haveArrayBuffer = typeof global.ArrayBuffer !== 'undefined'
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51
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var haveSlice = haveArrayBuffer && isFunction(global.ArrayBuffer.prototype.slice)
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52
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53
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// If fetch is supported, then arraybuffer will be supported too. Skip calling
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54
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// checkTypeSupport(), since that calls getXHR().
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55
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exports.arraybuffer = exports.fetch || (haveArrayBuffer && checkTypeSupport('arraybuffer'))
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56
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57
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// These next two tests unavoidably show warnings in Chrome. Since fetch will always
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58
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// be used if it's available, just return false for these to avoid the warnings.
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59
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exports.msstream = !exports.fetch && haveSlice && checkTypeSupport('ms-stream')
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60
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exports.mozchunkedarraybuffer = !exports.fetch && haveArrayBuffer &&
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61
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checkTypeSupport('moz-chunked-arraybuffer')
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62
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63
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// If fetch is supported, then overrideMimeType will be supported too. Skip calling
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64
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// getXHR().
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65
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exports.overrideMimeType = exports.fetch || (getXHR() ? isFunction(getXHR().overrideMimeType) : false)
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66
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67
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exports.vbArray = isFunction(global.VBArray)
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|
68
|
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69
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function isFunction (value) {
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70
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return typeof value === 'function'
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71
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}
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72
|
|
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73
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xhr = null // Help gc
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